I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years
old, and works well, until last night after I fell asleep.

(Please, no one tell me to get a new furnace. I've heard that before.
When I can, I will.)

I woke up early and the 2nd floor temp was 60 instead of 68.

Question 1: When the thermostat is set to auto, as it always is, the
air circulation fan goes on about a minute after the furnace starts. In
a furnace of this age, is that because of the Fan and Limit Control????
As opposed to something on the small control board, which has only about
15 resistors, capacitors, transistors, including 2 relays.

Question 2: Does the Fan and Limit Control keep the furnace running
once it reaches fan termperature (and until the thermostat says for it
to stop.)? I would think the answer is No, and that the control board
alone starts the furnace and keeps it running, until the thermostat says
no.


To try to get the furnace going, I pressed the reset button, but it
didn't need to be reset. I checked the circuit breaker; measured the
voltage on the secondary of the power transformer, and removed the
control box cover, just in case anything cried out, "I'm broken".

Besides the relay with the reset button, there is another relay next to
it, about 3/4" cubed. I pressed the armature down and the furnace
started. Let go after 3 seconds and it stopped.

Thought about checking out the thermostat, but didn't know what color
wires were used for heat. Thought about replacing the whole control
circuit board, but figured I'd better test the thermostat first.

To get some heat until I could learn wire colors and maybe replace the
thermostat, thought I'd jam a piece of wood between the relay armature
and something above it. Didn't find the right length of wood, but even
a shorter piece was heavy enough to hold down the armature, just leaning
against the cabinet.

That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet?? I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

I'm 99% sure it will turn off when the house is warm, but not at all
sure it will restart when it should.

Any suggestions, other than getting a new furnace?

On 02/11/2014 06:56 AM, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years
old, and works well, until last night after I fell asleep.

(Please, no one tell me to get a new furnace. I've heard that before.
When I can, I will.)

I


I'm sure it's fixable but really

why don't you get a high efficiency gas furnace?


When I got rid of my oil burner and went to gas I saved so much money it
was well worth it.

It paid for itself within two years.

On Tuesday, February 11, 2014 7:58:44 AM UTC-6, philo* wrote:
philo, the key here is:

When I can, I will.

On 2/11/2014 7:56 AM, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years
old, and works well, until last night after I fell asleep.

SM: Night, colder, furnace works harder.

(Please, no one tell me to get a new furnace. I've heard that before.
When I can, I will.)

I woke up early and the 2nd floor temp was 60 instead of 68.

Question 1: When the thermostat is set to auto, as it always is, the
air circulation fan goes on about a minute after the furnace starts. In
a furnace of this age, is that because of the Fan and Limit Control????
As opposed to something on the small control board, which has only about
15 resistors, capacitors, transistors, including 2 relays.

SM: Can be either.

Question 2: Does the Fan and Limit Control keep the furnace running
once it reaches fan termperature (and until the thermostat says for it
to stop.)? I would think the answer is No, and that the control board
alone starts the furnace and keeps it running, until the thermostat says
no.

SM: No, typically not.



To try to get the furnace going, I pressed the reset button, but it
didn't need to be reset. I checked the circuit breaker; measured the
voltage on the secondary of the power transformer, and removed the
control box cover, just in case anything cried out, "I'm broken".

SM: Amazing, what you can find with a good look see.


Besides the relay with the reset button, there is another relay next to
it, about 3/4" cubed. I pressed the armature down and the furnace
started. Let go after 3 seconds and it stopped.

SM: Blower fan, or burner assembly started?


Thought about checking out the thermostat, but didn't know what color
wires were used for heat. Thought about replacing the whole control
circuit board, but figured I'd better test the thermostat first.

SM: No sense throwing parts at it.


To get some heat until I could learn wire colors and maybe replace the
thermostat, thought I'd jam a piece of wood between the relay armature
and something above it. Didn't find the right length of wood, but even
a shorter piece was heavy enough to hold down the armature, just leaning
against the cabinet.

That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!.

SM: Started the furnace. You mean the burner gun, or the air handler
blower? I guess if the fan didn't start, which fan was that? The air
handler fan?


Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet??

SM: Typically the fan limit does two things. Turns the air handler fan
on when the fire box is hot. turns the burner off, if the firebox is too
hot.

I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

I'm 99% sure it will turn off when the house is warm, but not at all
sure it will restart when it should.

Any suggestions, other than getting a new furnace?

SM: Call a repair and service company. Hard to diagnose from here.

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Tuesday, February 11, 2014 7:56:18 AM UTC-5, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years

old, and works well, until last night after I fell asleep.



(Please, no one tell me to get a new furnace. I've heard that before.

When I can, I will.)



I woke up early and the 2nd floor temp was 60 instead of 68.



Question 1: When the thermostat is set to auto, as it always is, the

air circulation fan goes on about a minute after the furnace starts. In

a furnace of this age, is that because of the Fan and Limit Control????

In the old ones I've seen, yes. Temp switch in the plenum turns
on the fan when it gets hot, shuts it off when it gets cool.



As opposed to something on the small control board, which has only about

15 resistors, capacitors, transistors, including 2 relays.



Question 2: Does the Fan and Limit Control keep the furnace running

once it reaches fan termperature (and until the thermostat says for it

to stop.)? I would think the answer is No, and that the control board

alone starts the furnace and keeps it running, until the thermostat says

no.



I'd say that's kind of right. The limit switch does form
part of the circuit that keeps it running though. If the temp gets
too high, it shuts it down.







To try to get the furnace going, I pressed the reset button, but it

didn't need to be reset. I checked the circuit breaker; measured the

voltage on the secondary of the power transformer, and removed the

control box cover, just in case anything cried out, "I'm broken".



Besides the relay with the reset button, there is another relay next to

it, about 3/4" cubed. I pressed the armature down and the furnace

started. Let go after 3 seconds and it stopped.


Thought about checking out the thermostat, but didn't know what color

wires were used for heat.

Red is power, white is heat, yellow is AC, green is fan.
That's the usual convention. So for heat, connect red to white.



Thought about replacing the whole control

circuit board, but figured I'd better test the thermostat first.



To get some heat until I could learn wire colors and maybe replace the

thermostat, thought I'd jam a piece of wood between the relay armature

and something above it. Didn't find the right length of wood, but even

a shorter piece was heavy enough to hold down the armature, just leaning

against the cabinet.


Without knowing exactly what that relay button bypasses, I
sure wouldn't jamb it closed with a stick.





That started the furnace and immediately I thought, "Will the house fan

start? Can't run the furnace for long without the fan" Ran for about 3

minutes but didn't hear the fan start, so I removed the piece of wood.

Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo

Carrier keep the furnace running once it gets hot enough but the

thermostat hasn't said Stop yet?? I thought not, but the furnace is

still running. If the answer really is NO, something has changed since

the furnace didn't run all night.


I had to leave the furnace room to find an air vent, and indeed, the fan

is blowing.



I'm 99% sure it will turn off when the house is warm, but not at all

sure it will restart when it should.



Any suggestions, other than getting a new furnace?

Find a schematic that shows the controls, how they are wired,
and proceed with the debugging. Or call for service.

Micky,

Do you have a circuit diagram? Have you checked the relay that is no
longer closing? Is there power to the relay? Is the coil of the relay fried?

Dave M.
ce?

On 2/11/2014 7:56 AM, micky wrote:
That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet?? I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

Since you forced the burner on, but the air
handler blower didn't come on, makes me wonder
if the fan limit switch is open, and reading
high temp overlimit?

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On 02/11/2014 08:02 AM, Bob_Villa wrote:
On Tuesday, February 11, 2014 7:58:44 AM UTC-6, philo wrote:
philo, the key here is:

When I can, I will.



He can do it today

On Tue, 11 Feb 2014 10:51:35 -0500, Stormin Mormon
wrote:

On 2/11/2014 7:56 AM, micky wrote:
That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet?? I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

Since you forced the burner on, but the air
handler blower didn't come on,

No, it did come on. See my two line paragraph above. I didn't *hear*
it come on when I was standing right next to the furnace. Too much
noise there.


makes me wonder
if the fan limit switch is open, and reading
high temp overlimit?

On Tue, 11 Feb 2014 09:31:23 -0500, Stormin Mormon
wrote:

On 2/11/2014 7:56 AM, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years
old, and works well, until last night after I fell asleep.

SM: Night, colder, furnace works harder.

(Please, no one tell me to get a new furnace. I've heard that before.
When I can, I will.)

I woke up early and the 2nd floor temp was 60 instead of 68.

Question 1: When the thermostat is set to auto, as it always is, the
air circulation fan goes on about a minute after the furnace starts. In
a furnace of this age, is that because of the Fan and Limit Control????
As opposed to something on the small control board, which has only about
15 resistors, capacitors, transistors, including 2 relays.

SM: Can be either.

Question 2: Does the Fan and Limit Control keep the furnace running
once it reaches fan termperature (and until the thermostat says for it
to stop.)? I would think the answer is No, and that the control board
alone starts the furnace and keeps it running, until the thermostat says
no.

SM: No, typically not.



To try to get the furnace going, I pressed the reset button, but it
didn't need to be reset. I checked the circuit breaker; measured the
voltage on the secondary of the power transformer, and removed the
control box cover, just in case anything cried out, "I'm broken".

SM: Amazing, what you can find with a good look see.


Besides the relay with the reset button, there is another relay next to
it, about 3/4" cubed. I pressed the armature down and the furnace
started. Let go after 3 seconds and it stopped.

SM: Blower fan, or burner assembly started?

Only the oil pump and the fan on the same motor started, and the
ignition. That's all that normally starts. Later, the big air fan
turns on.


Thought about checking out the thermostat, but didn't know what color
wires were used for heat. Thought about replacing the whole control
circuit board, but figured I'd better test the thermostat first.

SM: No sense throwing parts at it.


To get some heat until I could learn wire colors and maybe replace the
thermostat, thought I'd jam a piece of wood between the relay armature
and something above it. Didn't find the right length of wood, but even
a shorter piece was heavy enough to hold down the armature, just leaning
against the cabinet.

That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!.

SM: Started the furnace. You mean the burner gun, or the air handler
blower? I guess if the fan didn't start, which fan was that? The air
handler fan?

I hate that term "air handler". What did they call it before air
conditioning? But yeah, that's what I was referring to but it did
start. I just didn't hear it.


Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet??

SM: Typically the fan limit does two things. Turns the air handler fan
on when the fire box is hot. turns the burner off, if the firebox is too
hot.

I guess I thought about the second but not about the first, until today.

Thanks.

On Tue, 11 Feb 2014 10:36:16 -0500, "David L. Martel"
wrote:

Micky,

Do you have a circuit diagram?

I'd forgotten that the owners manual included a both a wiring schematic
and a wiring diagram, they call them. The second is laid out more like
in real life, with things that are physically close being close on the
diagram.

The diagram is hard for me to understand because I'm used to pure
electronics diagrams. Or maybe it's because they updated things before
ending this model. I got this off the web, but I need to find the paper
manual that came with the furnace, which will match the furnace exactly.

(For example, the online disagram shows things running off the center
tap of the secondary, but when I had to replace the transformer 30 years
ago, nothing was connected to the center tap. The online manual shows
a solid state switch, intead of two mechanical relays. It shows no reset
button (which is mechanical, not electric exactly, but would still be
indicated if they were still using one.

(It shows that the air fan is on high for AC and one of three setting
for heat, but mine uses the same speed for AC and heat, I'm 99% sure.

(The online manual seems to indicate one resistor, marked 1K, but it
also shows a set of contact poitns or a capacitor marked 1K2 !! 1K and
1K2 might be the missing relay, but I really need to find my paper
owners manual.

Have you checked the relay that is no
longer closing? Is there power to the relay?

I havent' checked that. Good point. Probably not.

Is the coil of the relay fried?

I doubt it because the armature stayed down after I held it down for a
couple minutes. And the furnace turned off when the second floor
temp was 66, so after another test, I pushed the armature down again,
(maybe on the right side instead of the left and probably farther than
the first time, when it was just 3 seconds) and this time I heard it
click, like the armature hitting the coil, and it stayed down from the
beginning. So I think that's the coil holding it in.

(Hmm. The furnace just stopped. Upstairs temp is just 70 degrees (It's
usually warmer than the first floor. ))

The test I made was jumping the thermostat connections at the furnace
and that didn't start it up. I think that means the thermostat is okay,
Or at least there is a problem with the control board, but to be sure I
want to disconnect the stat and measure the resistance between those
wires when the house is warm and when it is cold. Can't do it when the
thermostat's connected because there are 24 volts between those
wires/screws.

If it's not the thermostat, it's the control board, and I have a spare
one from the identical burner a neighbor replaced. (Well I think
it's identical. When I take the cover off the control board, it might
match the online wiring diagram.)

Since the current control board has only 2 resistors, one capacitor, 2
transistors, and 2 relays, maybe I could fix it, but exchanging it is
easier. Maybe I'll try to fix the old one then.


Dave M.
ce?

On Tue, 11 Feb 2014 06:43:04 -0800 (PST), "
wrote:

On Tuesday, February 11, 2014 7:56:18 AM UTC-5, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years

old, and works well, until last night after I fell asleep.



(Please, no one tell me to get a new furnace. I've heard that before.

When I can, I will.)



I woke up early and the 2nd floor temp was 60 instead of 68.



Question 1: When the thermostat is set to auto, as it always is, the

air circulation fan goes on about a minute after the furnace starts. In

a furnace of this age, is that because of the Fan and Limit Control????

In the old ones I've seen, yes. Temp switch in the plenum turns
on the fan when it gets hot, shuts it off when it gets cool.

Makes sense now. Where else would it be? But I just figured it was a
mystery box.

As opposed to something on the small control board, which has only about

15 resistors, capacitors, transistors, including 2 relays.

When I counted, my imagination was way off. There were only 2
resistors, 1 capacitor, 2 transistors, and 2 relays.
....

Thought about checking out the thermostat, but didn't know what color

wires were used for heat.

Red is power, white is heat, yellow is AC, green is fan.
That's the usual convention. So for heat, connect red to white.

Thanks. That helps.



To get some heat until I could learn wire colors and maybe replace the

thermostat, thought I'd jam a piece of wood between the relay armature

and something above it. Didn't find the right length of wood, but even

a shorter piece was heavy enough to hold down the armature, just leaning

against the cabinet.


Without knowing exactly what that relay button bypasses, I
sure wouldn't jamb it closed with a stick.

Well, I was standing right there, and I took the stick off after 3
minutes, to keep the firebox from overheating, but (it stayed on and)
when I went to a quieter room, I could hear the "air handler" blowing
and next I found a a vent within reach where I could feel the air
blowing.
.....

I'm 99% sure it will turn off when the house is warm, but not at all

sure it will restart when it should.

It didn't.


Any suggestions, other than getting a new furnace?

Find a schematic that shows the controls, how they are wired,
and proceed with the debugging.

The manual I found online has been good for specs, but the schematic has
too many discrepancies from my furnace, even though it's the same model
number. The one online is probably the final schematic and mine
wasn't. I see that in tvs too. I'll look for my paper copy that
actually came with the furnace.

On Tue, 11 Feb 2014 07:56:18 -0500, micky
wrote:

I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years
old, and works well, until last night after I fell asleep.

(Please, no one tell me to get a new furnace. I've heard that before.
When I can, I will.)

I woke up early and the 2nd floor temp was 60 instead of 68.

With your help, I've made a lot of progress on the furnace, but I have a
paradox, I think.

All of these steps done when the house was cold again.

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.

B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course. Measured the resistance it
was over 100,000 ohms. Confirmation.

OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.

C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

A and B indicate a bad thermostat. C indicates a bad furnace.
Specifally, a bad furnace control board because other tests have
excluded everything else.

I just don't believe they both failed the same night.

BTW, the furnace control board only has 2 resistors, 1 ceramic disc
capacitor, 2 transistors, and 2 relays***.

Any suggestions or corrections?


***I have found in the "schematic" the black relay whose armature I've
pushed to start the furnace. It is labeled "limit switch" and it
interrupts the 110 volts to the whole control board and the motors and
ignition transformer. But the wiring "diagram" on the same page for my
model shows another limit switch in the fan and limit control, a
separate box that extends iiuc into the firebox. No wonder I'm
confused.

The second relay might not be a relay exactly. It works with the
cadmium photo cell to turn the furnace off if there is no flame in the
firebox, like if the furnace runs out of oil. And maybe if the firebox
gets too hot. I don't know. I've never had that particular problem.

On Tue, 11 Feb 2014 13:23:49 -0500, micky
wrote:

On Tue, 11 Feb 2014 06:43:04 -0800 (PST), "
wrote:

On Tuesday, February 11, 2014 7:56:18 AM UTC-5, micky wrote:
I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years

old, and works well, until last night after I fell asleep.



(Please, no one tell me to get a new furnace. I've heard that before.

When I can, I will.)



I woke up early and the 2nd floor temp was 60 instead of 68.



Question 1: When the thermostat is set to auto, as it always is, the

air circulation fan goes on about a minute after the furnace starts. In

a furnace of this age, is that because of the Fan and Limit Control????

In the old ones I've seen, yes. Temp switch in the plenum turns
on the fan when it gets hot, shuts it off when it gets cool.

Makes sense now. Where else would it be? But I just figured it was a
mystery box.

As opposed to something on the small control board, which has only about

15 resistors, capacitors, transistors, including 2 relays.

When I counted, my imagination was way off. There were only 2
resistors, 1 capacitor, 2 transistors, and 2 relays.
....

Thought about checking out the thermostat, but didn't know what color

wires were used for heat.

Red is power, white is heat, yellow is AC, green is fan.
That's the usual convention. So for heat, connect red to white.

Thanks. That helps.



To get some heat until I could learn wire colors and maybe replace the

thermostat, thought I'd jam a piece of wood between the relay armature

and something above it. Didn't find the right length of wood, but even

a shorter piece was heavy enough to hold down the armature, just leaning

against the cabinet.


Without knowing exactly what that relay button bypasses, I
sure wouldn't jamb it closed with a stick.

Well, I was standing right there, and I took the stick off after 3
minutes, to keep the firebox from overheating, but (it stayed on and)
when I went to a quieter room, I could hear the "air handler" blowing
and next I found a a vent within reach where I could feel the air
blowing.
.....

I'm 99% sure it will turn off when the house is warm, but not at all

sure it will restart when it should.

It didn't.


Any suggestions, other than getting a new furnace?

Find a schematic that shows the controls, how they are wired,
and proceed with the debugging.

The manual I found online has been good for specs, but the schematic has
too many discrepancies from my furnace, even though it's the same model
number. The one online is probably the final schematic and mine
wasn't. I see that in tvs too. I'll look for my paper copy that
actually came with the furnace.
A relay coil can fail in such a way as to be able to hold a contact
closed, but not be able to PULL it closed. Check the relay coil. Also
check the control transformer voltage. If it is supposed to be 24 and
it is only 16, the reays are not going to function properly. Also
check the wires for high resistance.

On 2/11/2014 1:14 PM, micky wrote:
On Tue, 11 Feb 2014 10:51:35 -0500, Stormin Mormon
wrote:

On 2/11/2014 7:56 AM, micky wrote:
That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet?? I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

Since you forced the burner on, but the air
handler blower didn't come on,

No, it did come on. See my two line paragraph above. I didn't *hear*
it come on when I was standing right next to the furnace. Too much
noise there.


Ah, that makes more sense. Thanks.
--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Tue, 11 Feb 2014 19:13:52 -0500, Stormin Mormon
wrote:

On 2/11/2014 1:14 PM, micky wrote:
On Tue, 11 Feb 2014 10:51:35 -0500, Stormin Mormon
wrote:

On 2/11/2014 7:56 AM, micky wrote:
That started the furnace and immediately I thought, "Will the house fan
start? Can't run the furnace for long without the fan" Ran for about 3
minutes but didn't hear the fan start, so I removed the piece of wood.
Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet?? I thought not, but the furnace is
still running. If the answer really is NO, something has changed since
the furnace didn't run all night.

I had to leave the furnace room to find an air vent, and indeed, the fan
is blowing.

Since you forced the burner on, but the air
handler blower didn't come on,

No, it did come on. See my two line paragraph above. I didn't *hear*
it come on when I was standing right next to the furnace. Too much
noise there.


Ah, that makes more sense. Thanks.

And by the way, the stuff I had for salting sidewalks that turned into a
glob was calcium chloride, like you thought.

Very different from my 50 pound bag of CaCl2, which never turned into a
glob (though I had it less than a year, not 10 or 15 like this) , and
which had a big puddle of water at the bottom and on the other side of
the separator,( not like this which had no water, but was in a capped
container, but otoh, has cracks in the container from age. I should
tape them.)

micky,

\ All of these steps done when the house was cold again.

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.

Yes, the thermostat is open. What is the setting of the thermostat?
Should it be open or closed? Set the temp to 50 and it should be open,
unless your house is really cold. Set it to 85 and it should be closed.

B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course.

What? You have 24v across the wires when they are connected to the
thermostat but not when they are disconnected from the thermostat? This
makes no sense to me.

Measured the resistance it
was over 100,000 ohms. Confirmation.

You've lost me. What are you confirming? Are you measuring the resistance
across the thermostat? Is the thermostat open or closed? Set the thermostat
really hot (80 or 90). Be sure that the stat is set for heat That should
close the switch. You should get a very low resistance

OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.

Yes, if the thermostat is open it is not calling for heat. Look you
aren't being very clear. Should the thermostat be calling for heat? Please
tell us the temp setting for the thermostat and confirm that the stat is set
for heat.

C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

Is there 24v across these wires before they are connected?



Dave M.

On Tue, 11 Feb 2014 20:14:03 -0500, "David L. Martel"
wrote:

micky,

\ All of these steps done when the house was cold again.

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.

Yes, the thermostat is open. What is the setting of the thermostat?
Should it be open or closed? Set the temp to 50 and it should be open,
unless your house is really cold. Set it to 85 and it should be closed.

B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course.

What? You have 24v across the wires when they are connected to the
thermostat but not when they are disconnected from the thermostat? This
makes no sense to me.

I'm sorry. The furnace, not the thermostat. No voltage between the
thermostat wires when one wire is disconnected from the *furnace*, not
the thermostat, I'm standing at the furnace and disconnecting the wire
there. . The thermostat itself is where it's always been, but it is
almost inaccessible right now, since I hurt my back.


Measured the resistance it
was over 100,000 ohms. Confirmation.

You've lost me. What are you confirming?

That the thermostat switch is open.

Are you measuring the resistance
across the thermostat?

Yes. One wire, red still screwed to the furnace control board and one
wire, white, unscrewed from it. Plus I checked which screws get the
thermostat wires, and those are it.

Is the thermostat open or closed?

It should have been closed then because the house was cold at the time,
maybe 58 degrees when the stat is set at 68 and normally keeps the house
at 68.

But when I measure the resistance between the two wires from the
thermostat, it is over 100,000 ohms. It's not closed when it should be
closed.

Set the thermostat
really hot (80 or 90). Be sure that the stat is set for heat That should
close the switch. You should get a very low resistance

Well I can't reset the thermostat until I get access. Requires some
heavy lifting. Probably need a friend.

OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.

Yes, if the thermostat is open it is not calling for heat. Look you
aren't being very clear. Should the thermostat be calling for heat? Please
tell us the temp setting for the thermostat and confirm that the stat is set
for heat.

Set at 68 and set to call for heat. I havent changed that in years.
(The AC is broken and during the late-spring, summer, early fall I just
turn off the power to the furnace, so it doesn't start on a cold night.)

C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

Is there 24v across these wires before they are connected?

There was a couple minutes earlier, when I did test 1, And I measure
it earlier too and also got 24v. So a jumper from one screw to
another should start the furnace. But it doesn't start.

Sorry I was confusing.


Dave M.

On Tue, 11 Feb 2014 19:03:04 -0500, wrote:


A relay coil can fail in such a way as to be able to hold a contact
closed, but not be able to PULL it closed. Check the relay coil. Also
check the control transformer voltage. If it is supposed to be 24 and
it is only 16, the reays are not going to function properly. Also
check the wires for high resistance.

Will do.

On 2/11/2014 1:19 PM, micky wrote:

Does the Fan and Limit Control on a 34 yo
Carrier keep the furnace running once it gets hot enough but the
thermostat hasn't said Stop yet??

SM: Typically the fan limit does two things. Turns the air handler fan
on when the fire box is hot. turns the burner off, if the firebox is too
hot.

I guess I thought about the second but not about the first, until today.

Thanks.


My pleasure. BTW, did you get it repaired?

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Tuesday, February 11, 2014 6:52:50 PM UTC-5, micky wrote:
On Tue, 11 Feb 2014 07:56:18 -0500, micky

wrote:



I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years

old, and works well, until last night after I fell asleep.



(Please, no one tell me to get a new furnace. I've heard that before.

When I can, I will.)



I woke up early and the 2nd floor temp was 60 instead of 68.



With your help, I've made a lot of progress on the furnace, but I have a

paradox, I think.



All of these steps done when the house was cold again.



A) When the thermostat wires for heat are connected to the thermostat

screws (for heat) on the furnace control board, there are 24VAC between

them. That alone means that the thermostatic switch in the thermostat

is open, or the voltage drop would be very close to zero.



Assuming you're on the right wires, I agree.




B) But to be sure, I disconnected one of the wires to the themostat,

measured the voltage between that wire and the other wire/screw (not

disconnected), and it was zero of course. Measured the resistance it

was over 100,000 ohms. Confirmation.


Again, if you're indeed on the wires that go to the
thermostat, then either there is a break in the wiring
or the thermostat is bad.




OKay, so an open switch means the thermostat is not calling for heat,

even when it is cold in the house.



C) Then I jump the two screws on the furnace control board where the

thermostat is connected (the same two I've been working with above.)

Jumping them should call for heat but the furnace doesn't start!!



A and B indicate a bad thermostat. C indicates a bad furnace.

Specifally, a bad furnace control board because other tests have

excluded everything else.



I just don't believe they both failed the same night.



Seems unlikely.





BTW, the furnace control board only has 2 resistors, 1 ceramic disc

capacitor, 2 transistors, and 2 relays***.



Any suggestions or corrections?


You have 24V at the two contacts at the furnace that go
to the thermostat. Should be the red and white wires.
When you connect them together and the furnace doesn't start,
did you measure the output of the transformer? 24V there?

You could have a bad connection there in the furnace wiring.
If a connection was high resistance, you could see 24V
at the terminals, but when you connect them together,
enough current would not flow to close the relay.
Imagine the circuit being correctly working, but then
a 10K resistor is put in series (simulating the bad connection)
You'd still see 24V open circuit, but if you connect
the terminals not enough current will flow to close the
relay. Could also be some bad component too, eg the
relay coil, presenting a higher resistance than should
be there.

The other part, about the thermostat and/or wires going
to it, no more ideas on what's going on there.




***I have found in the "schematic" the black relay whose armature I've

pushed to start the furnace. It is labeled "limit switch" and it

interrupts the 110 volts to the whole control board and the motors and

ignition transformer. But the wiring "diagram" on the same page for my

model shows another limit switch in the fan and limit control, a

separate box that extends iiuc into the firebox. No wonder I'm

confused.



The second relay might not be a relay exactly. It works with the

cadmium photo cell to turn the furnace off if there is no flame in the

firebox, like if the furnace runs out of oil. And maybe if the firebox

gets too hot. I don't know. I've never had that particular problem.

On 2/11/2014 6:52 PM, micky wrote:

All of these steps done when the house was cold again.

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.
SM: Are you reading at the furnace? Between which two terminals?


B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course. Measured the resistance it
was over 100,000 ohms. Confirmation.
SM: Sounds like thermostat was open connection.


OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.

SM: So far, yes.


C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

SM: Were the screws on the furnace lettered? Probably R and W?


A and B indicate a bad thermostat. C indicates a bad furnace.
Specifally, a bad furnace control board because other tests have
excluded everything else.

I just don't believe they both failed the same night.

BTW, the furnace control board only has 2 resistors, 1 ceramic disc
capacitor, 2 transistors, and 2 relays***.

Any suggestions or corrections?

SM: Might be time to call a service company.



***I have found in the "schematic" the black relay whose armature I've
pushed to start the furnace. It is labeled "limit switch" and it
interrupts the 110 volts to the whole control board and the motors and
ignition transformer.

SM: Usually there for a reason. I'm not familiar enough with your model
of furnace to know which limit switch is this, adn what it detects.


But the wiring "diagram" on the same page for my
model shows another limit switch in the fan and limit control, a
separate box that extends iiuc into the firebox. No wonder I'm
confused.

SM: Furnace usually have several things that turn it off, and one that
turns it on. That's safety for you.



The second relay might not be a relay exactly. It works with the
cadmium photo cell to turn the furnace off if there is no flame in the
firebox, like if the furnace runs out of oil. And maybe if the firebox
gets too hot. I don't know. I've never had that particular problem.

SM: Can't see it from here.

On 2/11/2014 8:35 PM, micky wrote:
What? You have 24v across the wires when they are connected to the
thermostat but not when they are disconnected from the thermostat? This
makes no sense to me.

I'm sorry. The furnace, not the thermostat. No voltage between the
thermostat wires when one wire is disconnected from the *furnace*, not
the thermostat, I'm standing at the furnace and disconnecting the wire
there. . The thermostat itself is where it's always been, but it is
almost inaccessible right now, since I hurt my back.

SM: If you have no volts at R and W or R and C at the furnace, you may
have a bad fuse or bad transformer.

Set the thermostat
really hot (80 or 90). Be sure that the stat is set for heat That should
close the switch. You should get a very low resistance

Well I can't reset the thermostat until I get access. Requires some
heavy lifting. Probably need a friend.

SM: What's with that? BEhind furniture?


Is there 24v across these wires before they are connected?

There was a couple minutes earlier, when I did test 1, And I measure
it earlier too and also got 24v. So a jumper from one screw to
another should start the furnace. But it doesn't start.

Sorry I was confusing.

SM: If 24 VAC from R to W, then the transformer is good. And the low
voltage fuse.


--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Wednesday, February 12, 2014 11:27:00 AM UTC-5, Stormin Mormon wrote:
On 2/11/2014 6:52 PM, micky wrote:



All of these steps done when the house was cold again.



A) When the thermostat wires for heat are connected to the thermostat

screws (for heat) on the furnace control board, there are 24VAC between

them. That alone means that the thermostatic switch in the thermostat

is open, or the voltage drop would be very close to zero.

SM: Are you reading at the furnace? Between which two terminals?





B) But to be sure, I disconnected one of the wires to the themostat,

measured the voltage between that wire and the other wire/screw (not

disconnected), and it was zero of course. Measured the resistance it

was over 100,000 ohms. Confirmation.

SM: Sounds like thermostat was open connection.





OKay, so an open switch means the thermostat is not calling for heat,

even when it is cold in the house.



SM: So far, yes.





C) Then I jump the two screws on the furnace control board where the

thermostat is connected (the same two I've been working with above.)

Jumping them should call for heat but the furnace doesn't start!!



SM: Were the screws on the furnace lettered? Probably R and W?





A and B indicate a bad thermostat. C indicates a bad furnace.

Specifally, a bad furnace control board because other tests have

excluded everything else.



I just don't believe they both failed the same night.



BTW, the furnace control board only has 2 resistors, 1 ceramic disc

capacitor, 2 transistors, and 2 relays***.



Any suggestions or corrections?



SM: Might be time to call a service company.







***I have found in the "schematic" the black relay whose armature I've

pushed to start the furnace. It is labeled "limit switch" and it

interrupts the 110 volts to the whole control board and the motors and

ignition transformer.



SM: Usually there for a reason. I'm not familiar enough with your model

of furnace to know which limit switch is this, adn what it detects.


Since pressing that started the furnace and kept it going,
it would seem to me
that either some sensor is telling the control board to shut down
or the control board is bad. A faulty flame sensor would be
a prime culprit.

The other part, where he's saying the thermostat wires at the
furnace indicate an open, don't know what to say about that.
Operator error perhaps?

On Wed, 12 Feb 2014 11:27:00 -0500, Stormin Mormon
wrote:

On 2/11/2014 6:52 PM, micky wrote:

All of these steps done when the house was cold again.

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
them. That alone means that the thermostatic switch in the thermostat
is open, or the voltage drop would be very close to zero.
SM: Are you reading at the furnace? Between which two terminals?

Yes. R & W.


B) But to be sure, I disconnected one of the wires to the themostat,
measured the voltage between that wire and the other wire/screw (not
disconnected), and it was zero of course. Measured the resistance it
was over 100,000 ohms. Confirmation.
SM: Sounds like thermostat was open connection.


OKay, so an open switch means the thermostat is not calling for heat,
even when it is cold in the house.

SM: So far, yes.


C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

SM: Were the screws on the furnace lettered? Probably R and W?

Yes.

A and B indicate a bad thermostat. C indicates a bad furnace.
Specifally, a bad furnace control board because other tests have
excluded everything else.

I just don't believe they both failed the same night.

BTW, the furnace control board only has 2 resistors, 1 ceramic disc
capacitor, 2 transistors, and 2 relays***.

Any suggestions or corrections?

SM: Might be time to call a service company.

Not yet. Probably not ever. I have the house's original thermostat,
and I have a replacement control panel, from the same model furnace.
One of those, or both, will make it work. But I just can't believe
they both failed in the same night.

I'm trying to think of something that could account for the apparent
failure of both the stat and the control panel, but I can't.


***I have found in the "schematic" the black relay whose armature I've
pushed to start the furnace. It is labeled "limit switch" and it
interrupts the 110 volts to the whole control board and the motors and
ignition transformer.

SM: Usually there for a reason. I'm not familiar enough with your model
of furnace to know which limit switch is this, adn what it detects.


But the wiring "diagram" on the same page for my
model shows another limit switch in the fan and limit control, a
separate box that extends iiuc into the firebox. No wonder I'm
confused.

SM: Furnace usually have several things that turn it off, and one that
turns it on. That's safety for you.

They should use different names.


The second relay might not be a relay exactly. It works with the
cadmium photo cell to turn the furnace off if there is no flame in the
firebox, like if the furnace runs out of oil. And maybe if the firebox
gets too hot. I don't know. I've never had that particular problem.

SM: Can't see it from here.

Let me hold it up to the screen. Better?

For now, I"ll run the furnace manually 2 or 3 times a day for a couple
hours a day, or whatever it takes I was able to get the house to 79,
then turn off the furnace for at least 10 hours and it was still 64. So
I can sleep all night. I need time to think and I'll figure out what's
wrong in a day or two.

On Wed, 12 Feb 2014 07:37:30 -0800 (PST), "
wrote:

On Tuesday, February 11, 2014 6:52:50 PM UTC-5, micky wrote:
On Tue, 11 Feb 2014 07:56:18 -0500, micky

wrote:



I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years

old, and works well, until last night after I fell asleep.



(Please, no one tell me to get a new furnace. I've heard that before.

When I can, I will.)



I woke up early and the 2nd floor temp was 60 instead of 68.



With your help, I've made a lot of progress on the furnace, but I have a

paradox, I think.



All of these steps done when the house was cold again.



A) When the thermostat wires for heat are connected to the thermostat

screws (for heat) on the furnace control board, there are 24VAC between

them. That alone means that the thermostatic switch in the thermostat

is open, or the voltage drop would be very close to zero.



Assuming you're on the right wires, I agree.




B) But to be sure, I disconnected one of the wires to the themostat,

measured the voltage between that wire and the other wire/screw (not

disconnected), and it was zero of course. Measured the resistance it

was over 100,000 ohms. Confirmation.


Again, if you're indeed on the wires that go to the
thermostat, then either there is a break in the wiring
or the thermostat is bad.

Definitely the right wires.




OKay, so an open switch means the thermostat is not calling for heat,

even when it is cold in the house.



C) Then I jump the two screws on the furnace control board where the

thermostat is connected (the same two I've been working with above.)

Jumping them should call for heat but the furnace doesn't start!!



A and B indicate a bad thermostat. C indicates a bad furnace.

Specifally, a bad furnace control board because other tests have

excluded everything else.



I just don't believe they both failed the same night.



Seems unlikely.


FWIW, the handles on two of my toilets failed within 3 months of each
other, after 34 years. I have to check the third toilet, that I don't
use. But that's still not the same night.



BTW, the furnace control board only has 2 resistors, 1 ceramic disc
capacitor, 2 transistors, and 2 relays***.



Any suggestions or corrections?


You have 24V at the two contacts at the furnace that go
to the thermostat. Should be the red and white wires.
When you connect them together and the furnace doesn't start,
did you measure the output of the transformer? 24V there?

I measured it with no load. You're right, I should measure again with a
load.

A lot of the places I'd like to take measurements from are not
available. The circuit board is in a metal box, a half inch about the
metal bottom.

I have insulation piercing alligator clips, for testing. Maybe I'll try
those. (In high school I had to use an ice pick, but it was only 12
volts.)

Not sure whether to just change control boxes or to try to debug this
one.


I'm going to go eat lunch. Seems like a reasonable compromise.

You could have a bad connection there in the furnace wiring.
If a connection was high resistance, you could see 24V
at the terminals, but when you connect them together,
enough current would not flow to close the relay.
Imagine the circuit being correctly working, but then
a 10K resistor is put in series (simulating the bad connection)
You'd still see 24V open circuit, but if you connect
the terminals not enough current will flow to close the
relay. Could also be some bad component too, eg the
relay coil, presenting a higher resistance than should
be there.

The other part, about the thermostat and/or wires going
to it, no more ideas on what's going on there.

On Wednesday, February 12, 2014 12:02:07 PM UTC-5, micky wrote:
On Wed, 12 Feb 2014 11:27:00 -0500, Stormin Mormon

wrote:



On 2/11/2014 6:52 PM, micky wrote:



All of these steps done when the house was cold again.



A) When the thermostat wires for heat are connected to the thermostat

screws (for heat) on the furnace control board, there are 24VAC between

them. That alone means that the thermostatic switch in the thermostat

is open, or the voltage drop would be very close to zero.

SM: Are you reading at the furnace? Between which two terminals?



Yes. R & W.





B) But to be sure, I disconnected one of the wires to the themostat,

measured the voltage between that wire and the other wire/screw (not

disconnected), and it was zero of course. Measured the resistance it

was over 100,000 ohms. Confirmation.

SM: Sounds like thermostat was open connection.





OKay, so an open switch means the thermostat is not calling for heat,

even when it is cold in the house.



SM: So far, yes.





C) Then I jump the two screws on the furnace control board where the

thermostat is connected (the same two I've been working with above.)

Jumping them should call for heat but the furnace doesn't start!!



SM: Were the screws on the furnace lettered? Probably R and W?



Yes.



A and B indicate a bad thermostat. C indicates a bad furnace.

Specifally, a bad furnace control board because other tests have

excluded everything else.



I just don't believe they both failed the same night.



BTW, the furnace control board only has 2 resistors, 1 ceramic disc

capacitor, 2 transistors, and 2 relays***.



Any suggestions or corrections?



SM: Might be time to call a service company.



Not yet. Probably not ever. I have the house's original thermostat,

and I have a replacement control panel, from the same model furnace.

One of those, or both, will make it work. But I just can't believe

they both failed in the same night.



I'm trying to think of something that could account for the apparent

failure of both the stat and the control panel, but I can't.





***I have found in the "schematic" the black relay whose armature I've

pushed to start the furnace. It is labeled "limit switch" and it

interrupts the 110 volts to the whole control board and the motors and

ignition transformer.



SM: Usually there for a reason. I'm not familiar enough with your model

of furnace to know which limit switch is this, adn what it detects.





But the wiring "diagram" on the same page for my

model shows another limit switch in the fan and limit control, a

separate box that extends iiuc into the firebox. No wonder I'm

confused.



SM: Furnace usually have several things that turn it off, and one that

turns it on. That's safety for you.



They should use different names.





The second relay might not be a relay exactly. It works with the

cadmium photo cell to turn the furnace off if there is no flame in the

firebox, like if the furnace runs out of oil. And maybe if the firebox

gets too hot. I don't know. I've never had that particular problem.



SM: Can't see it from here.



Let me hold it up to the screen. Better?



For now, I"ll run the furnace manually 2 or 3 times a day for a couple

hours a day, or whatever it takes I was able to get the house to 79,

then turn off the furnace for at least 10 hours and it was still 64. So

I can sleep all night. I need time to think and I'll figure out what's

wrong in a day or two.


Maybe we should recap where you're at.

A - You say with the thermostat wires disconnected at the furnace,
you can connect a meter to those wires going back to the
thermostat and measure an open circuit, even
though it's cold and the thermostat should be calling for heat.
That's across the red and white wires, which were
connected to the R and W terminals, before you removed them.
Have you verified this? It's repeatable? You're sure the
meter is on the ohm or continuity setting? How many wires
go to the thermostat? 3? heat, fan, power? If you're
100% sure about this, then there is a problem with the
thermostat or the wiring going to it.

It's also a little weird that you said something about not
being able to get to the thermostat without moving furniture?
That limits the ability to diagnose.

B - You say that shorting the R and W terminals, the furnace
won't start.

C - You can get the furnace to fire up and run by holding
down that relay button. It's not clear, is that with the thermostat
wires disconnected and the terminals open? From the description
it sounds like that is some kind of limit relay, but it
seems odd to me that it would make the furnace start up by
pushing it, if there is no call for heat. Any relay, etc
I've seen that was marked as "limit" could cut it off if
something wasn't right, but would not make it fire if there
was no call for heat.


Have you looked at the flame sensor? Not dirty? With a
furnace like that I'd have spare nozzle, flame sensor, filter,
etc, ie the common cheap things that can go wrong.

Also, with years of experience with that furnace, I would
think you'd know what gets tripped by what, at least to
some extent. For example, if it starts up, no flame is
detected, it shuts down. What do you have to push to reset
it?

On Wed, 12 Feb 2014 08:44:35 -0800 (PST), "
wrote:


Since pressing that started the furnace and kept it going,
it would seem to me
that either some sensor is telling the control board to shut down
or the control board is bad. A faulty flame sensor would be
a prime culprit.

Very good idea. I've been ignoring the flame sensor, except to note
how it's connected on the schematic.

I can disconnect one lead and test if it's bad or not. It conducts
when light is sensed, I red. Cadmium sulfite "The resistance value
of an LDR becomes smaller, as the LDR is more and more exposed. The
material is usually cadmium sulfide, the dark resistance is 1.10 M ohm
resistor while the light resistance is about 75-300 ohm. LDR's have a
relatively slow response time." I"m sure disconnecting will still work,
though the Carrier diagram gives no explanation for the "flame detection
electronic network." It's just a "black box". Even t hough it's made
of clear plastic, I still have no idea how it works.

They're only $14 on Amazon, with lots of brackets, plus $5 shipping,
but I have a spare one fo them too.

The other part, where he's saying the thermostat wires at the
furnace indicate an open, don't know what to say about that.
Operator error perhaps?

Me? Never.

google is your friend and a picture is worth 1000 words


http://www.electrical-online.com/the...ing-explained/

Mark

A) When the thermostat wires for heat are connected to the thermostat
screws (for heat) on the furnace control board, there are 24VAC between
SM: Are you reading at the furnace? Between which two terminals?

Yes. R & W.

SM: That rules out the 24vac transformer gone bad.


C) Then I jump the two screws on the furnace control board where the
thermostat is connected (the same two I've been working with above.)
Jumping them should call for heat but the furnace doesn't start!!

SM: Were the screws on the furnace lettered? Probably R and W?

Yes.
SM: That is reasonable.

Any suggestions or corrections?

SM: Might be time to call a service company.

Not yet. Probably not ever. I have the house's original thermostat,
and I have a replacement control panel, from the same model furnace.
One of those, or both, will make it work. But I just can't believe
they both failed in the same night.

SM: Sometimes,one fails, and then "takes out" the other.


I'm trying to think of something that could account for the apparent
failure of both the stat and the control panel, but I can't.
SM: Cascade failure.


SM: Furnace usually have several things that turn it off, and one that
turns it on. That's safety for you.

They should use different names.

SM: I agree.


The second relay might not be a relay exactly. It works with the
cadmium photo cell to turn the furnace off if there is no flame in the
firebox, like if the furnace runs out of oil. And maybe if the firebox
gets too hot. I don't know. I've never had that particular problem.

SM: Can't see it from here.

Let me hold it up to the screen. Better?
SM: No, I've got the wrong glasses on.


For now, I"ll run the furnace manually 2 or 3 times a day for a couple
hours a day, or whatever it takes I was able to get the house to 79,
then turn off the furnace for at least 10 hours and it was still 64. So
I can sleep all night. I need time to think and I'll figure out what's
wrong in a day or two.

SM: I suspect you will. I'd be looking for safety
devices, and limit switches which may have been
activated.

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On 2/12/2014 12:12 PM, micky wrote:
I measured it with no load. You're right, I should measure again with a
load.

A lot of the places I'd like to take measurements from are not
available. The circuit board is in a metal box, a half inch about the
metal bottom.

I have insulation piercing alligator clips, for testing. Maybe I'll try
those. (In high school I had to use an ice pick, but it was only 12
volts.)

Not sure whether to just change control boxes or to try to debug this
one.


I'm going to go eat lunch. Seems like a reasonable compromise.

I'm suspecting a safety switch of some kind. Either
tripped with (or without ) cause.

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

A couple Sundays ago, at church we had a furnace
go down. Cold in that section of the building.
It had given trouble several times, and this
time they called in an outside company to look
at it. Sure enough, one of the safety switches
was just a bit out of place, and wasn't getting
activated like it ought have.

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Tue, 11 Feb 2014 19:03:04 -0500, wrote:


A relay coil can fail in such a way as to be able to hold a contact
closed, but not be able to PULL it closed. Check the relay coil. Also
check the control transformer voltage. If it is supposed to be 24 and
it is only 16, the reays are not going to function properly. Also
check the wires for high resistance.

Will do.

BTW, in the original thermostat, a round Honeywell that was so popular
for so long in the 60's and 70's (not the one I'm using now,) there
were some square sine waves circuit traces on the little round circuit
board, and I see something on the heating cooling wiring schematic that
seems to correspond.

On the schematic they are labeled HTG ANT and CLG ANT.

Do you all know anythihng about these?

On Sat, 15 Feb 2014 21:05:48 -0500, micky
wrote:

On Tue, 11 Feb 2014 19:03:04 -0500, wrote:


A relay coil can fail in such a way as to be able to hold a contact
closed, but not be able to PULL it closed. Check the relay coil. Also
check the control transformer voltage. If it is supposed to be 24 and
it is only 16, the reays are not going to function properly. Also
check the wires for high resistance.

Will do.

BTW, in the original thermostat, a round Honeywell that was so popular
for so long in the 60's and 70's (not the one I'm using now,) there
were some square sine waves circuit traces on the little round circuit
board, and I see something on the heating cooling wiring schematic that
seems to correspond.

On the schematic they are labeled HTG ANT and CLG ANT.

Do you all know anythihng about these?
Heating anticipator and cooling anticipator

On 2/15/2014 9:05 PM, micky wrote:
BTW, in the original thermostat, a round Honeywell that was so popular
for so long in the 60's and 70's (not the one I'm using now,) there
were some square sine waves circuit traces on the little round circuit
board, and I see something on the heating cooling wiring schematic that
seems to correspond.

On the schematic they are labeled HTG ANT and CLG ANT.

Do you all know anythihng about these?


I've got a pretty good guess. I've had to set the
old rounds, and yes, pretty sure I know.
--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On Sat, 15 Feb 2014 22:15:48 -0500, wrote:

On Sat, 15 Feb 2014 21:05:48 -0500, micky
wrote:

On Tue, 11 Feb 2014 19:03:04 -0500, wrote:


A relay coil can fail in such a way as to be able to hold a contact
closed, but not be able to PULL it closed. Check the relay coil. Also
check the control transformer voltage. If it is supposed to be 24 and
it is only 16, the reays are not going to function properly. Also
check the wires for high resistance.

Will do.

BTW, in the original thermostat, a round Honeywell that was so popular
for so long in the 60's and 70's (not the one I'm using now,) there
were some square sine waves circuit traces on the little round circuit
board, and I see something on the heating cooling wiring schematic that
seems to correspond.

On the schematic they are labeled HTG ANT and CLG ANT.

Do you all know anythihng about these?
Heating anticipator and cooling anticipator

Ah. I thought they were heating antenna and cooling antenna. Your
answer makes a lot more sense.

P&M because it's been two days and the group is busy.