I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

On Thursday, November 28, 2019 at 8:11:12 PM UTC-5, trader_4 wrote:
On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

Another question, what does it do when it's 66/68 and you just leave it?
Does it eventually come on? Does it go back on when it drops to 65?, etc.
Or does the compressor just stay off indefinitely? What was it doing just
before, was it maintaining 68? If so, then you'd think it must stay off
a long time when it's 40 outside for inside to drop two degrees.

On Thu, 28 Nov 2019 17:11:06 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

in the thermostat cable
The white wire calls for heat (W2 calls the toaster wire)
The green wire turns on the fan.
Yellow is AC
Going out to the condenser it is either an orange or blue wire that
turns on the reversing valve (manufacturer dependent)

In article ,
says...

Another question, what does it do when it's 66/68 and you just leave it?
Does it eventually come on? Does it go back on when it drops to 65?, etc.
Or does the compressor just stay off indefinitely? What was it doing just
before, was it maintaining 68? If so, then you'd think it must stay off
a long time when it's 40 outside for inside to drop two degrees.






I don't know how long it was off as it was 4 deg low when I got up this
morning.

If I leave the unit along, the air handler keeps blowing and the outside
unit never comes on. Last night the thermostat was set to 68 and the
inside air was 64.

To start with I went out side and checked the relay that turns on the
compresor and fan that blows on the outside coils. There was no power
on the coil. Pushing it in manually and the units motors ran while
manuallyh pushed in.

I cut off the power to the unit and 5 minuets later the power came back
on (load control from the power compay has that built in delay external
to the unit). Nothing any different.

Then went to the thermostat and set it to off. Waited about 2 minutes
and turned it back on. The unit started up and has been working fine
all day and to ten at night (which it is now).

On Thursday, November 28, 2019 at 9:41:03 PM UTC-5, wrote:
On Thu, 28 Nov 2019 17:11:06 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

in the thermostat cable
The white wire calls for heat (W2 calls the toaster wire)
The green wire turns on the fan.
Yellow is AC
Going out to the condenser it is either an orange or blue wire that
turns on the reversing valve (manufacturer dependent)

But when it calls for heat does the thermostat activate the W wire and
the G fan wire? Or just the W wire? With furnaces, it only activates
the W wire, the furnace then turns on the blower. The G wire in the
furnace application is if you want to manually put the blower on,
without heat. That matters with Ralph's problem. If it takes two wires
to work it, then it's possibly a thermostat problem or issue with the W
wire. If it just takes activating the W wire, then the thermostat and
wiring aren't the problem, because his blower is running. I guess regardless
I would get it set up so that I could measure the voltage at the W and
G terminals at the air handler control board when it's having the problem.
That might require taping over a cut off switch on a panel.

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.

In article ,
says...

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.



I worked for years as an electrician and instrument person at a large
plant, so doing the actual work and measurment ( I have all kinds of
test instruments at home) is no problem. I dealt with computer controled
equipment and some 480 volt 3 phase heaters that pulled about 300 amps.
Just knowing what to look for on this simple controller is my problem.

That thing just will not stay screwed up long enough to find the
problem. It only does it a few times in the winter. Just started a year
or two ago.

I did check the relay that powers the compressor and fan. It did not
have any power going to them. Pushing it in by hand (screwdriver)
starts them.

I may buy a control board off ebay. Seems that I looked into it last
year but did not follow up when I bought a spare capacitor and relay
just so I would have them at hand.

The board would be cheap compaired to calling the man. I learned my
lesson on that a few years back when I was charged about $ 350 just to
have the capacitor replaced.

On Friday, November 29, 2019 at 11:03:10 AM UTC-5, Ralph Mowery wrote:
In article ,
says...

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.



I worked for years as an electrician and instrument person at a large
plant, so doing the actual work and measurment ( I have all kinds of
test instruments at home) is no problem. I dealt with computer controled
equipment and some 480 volt 3 phase heaters that pulled about 300 amps.
Just knowing what to look for on this simple controller is my problem.

That thing just will not stay screwed up long enough to find the
problem. It only does it a few times in the winter. Just started a year
or two ago.

I did check the relay that powers the compressor and fan. It did not
have any power going to them. Pushing it in by hand (screwdriver)
starts them.

Don't you mean that it doesn't happen often enough? I thought you said
that once it gets into it's off mode, it just stays there until you
cycle power? At the very least, it must be staying like that for hours,
if not indefinitely.





I may buy a control board off ebay. Seems that I looked into it last
year but did not follow up when I bought a spare capacitor and relay
just so I would have them at hand.

The board would be cheap compaired to calling the man. I learned my
lesson on that a few years back when I was charged about $ 350 just to
have the capacitor replaced.

Exactly. And if you don't need it, you can resell it on Ebay and likely
get most of your money back. That's how I look at many parts purchases
today, when I'm not 100% that it's that part. It's one of the wonders of
the internet age. Twenty five years ago, if you bought a part like that
and you didn't need it, there was no way to sell it.

On Fri, 29 Nov 2019 07:01:57 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 9:41:03 PM UTC-5, wrote:
On Thu, 28 Nov 2019 17:11:06 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

in the thermostat cable
The white wire calls for heat (W2 calls the toaster wire)
The green wire turns on the fan.
Yellow is AC
Going out to the condenser it is either an orange or blue wire that
turns on the reversing valve (manufacturer dependent)

But when it calls for heat does the thermostat activate the W wire and
the G fan wire? Or just the W wire? With furnaces, it only activates
the W wire, the furnace then turns on the blower. The G wire in the
furnace application is if you want to manually put the blower on,
without heat. That matters with Ralph's problem. If it takes two wires
to work it, then it's possibly a thermostat problem or issue with the W
wire. If it just takes activating the W wire, then the thermostat and
wiring aren't the problem, because his blower is running. I guess regardless
I would get it set up so that I could measure the voltage at the W and
G terminals at the air handler control board when it's having the problem.
That might require taping over a cut off switch on a panel.

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work. I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats). He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.

On Fri, 29 Nov 2019 11:02:59 -0500, Ralph Mowery
wrote:

In article ,
says...

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.



I worked for years as an electrician and instrument person at a large
plant, so doing the actual work and measurment ( I have all kinds of
test instruments at home) is no problem. I dealt with computer controled
equipment and some 480 volt 3 phase heaters that pulled about 300 amps.
Just knowing what to look for on this simple controller is my problem.

That thing just will not stay screwed up long enough to find the
problem. It only does it a few times in the winter. Just started a year
or two ago.

I did check the relay that powers the compressor and fan. It did not
have any power going to them. Pushing it in by hand (screwdriver)
starts them.

I may buy a control board off ebay. Seems that I looked into it last
year but did not follow up when I bought a spare capacitor and relay
just so I would have them at hand.

The board would be cheap compaired to calling the man. I learned my
lesson on that a few years back when I was charged about $ 350 just to
have the capacitor replaced.

Since you do seem to have skills, it might be worth making up a test
light with an LED and a 2k or so resistor and hanging it on the white
wire and maybe another one on the green.. Then if that is OK start
moving it closer to the relay that is not getting the pick shot. You
can leave it connected and look at it when it is working, again when
it is failing. In a few failures, you should be able to find the bad
part.

In article ,
says...

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work. I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats). He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.



This is not a furnace, but a heat pump.

The fan on the air handler runs when it is calling for heat. It is the
out side unit that is not running. The relay for it has no voltage
going to the coil that tells it to pull in and run the compressor and
the fan for the outside coils.

The thing acts up so infrequent it is difficult for me to do much but
just want to get it started. I hate cold weather and seems like my
brain freezes up when cold. I call anyting below about 50 cold being in
the middle of NC.

On Friday, November 29, 2019 at 11:27:29 AM UTC-5, wrote:
On Fri, 29 Nov 2019 07:01:57 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 9:41:03 PM UTC-5, wrote:
On Thu, 28 Nov 2019 17:11:06 -0800 (PST), trader_4
wrote:

On Thursday, November 28, 2019 at 12:28:16 PM UTC-5, Ralph Mowery wrote:
I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?

IDK how heat pump systems call for heat. Is there one wire that says
make heat, another one that turns the blower on? Or does one wire say
make heat and the system turns the blower on? If it's the latter,
then since the blower is running you can rule out the thermostat.
If it's two wires, then it's possible it's a thermostat problem.

I agree that calling for service on something like this is really bad.
They won't see it happening and even if they do, probably won't have
any more idea what to do that you do.

in the thermostat cable
The white wire calls for heat (W2 calls the toaster wire)
The green wire turns on the fan.
Yellow is AC
Going out to the condenser it is either an orange or blue wire that
turns on the reversing valve (manufacturer dependent)

But when it calls for heat does the thermostat activate the W wire and
the G fan wire? Or just the W wire? With furnaces, it only activates
the W wire, the furnace then turns on the blower. The G wire in the
furnace application is if you want to manually put the blower on,
without heat. That matters with Ralph's problem. If it takes two wires
to work it, then it's possibly a thermostat problem or issue with the W
wire. If it just takes activating the W wire, then the thermostat and
wiring aren't the problem, because his blower is running. I guess regardless
I would get it set up so that I could measure the voltage at the W and
G terminals at the air handler control board when it's having the problem.
That might require taping over a cut off switch on a panel.

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work.

Furnace is as I described. The thermostat just calls for heat on the W
wire (or wires if it's two stage), the furnace does the rest, ie turns
the blower on after the furnace has fired for a minute or so. Old
furnaces used to use a temp switch in the plenum to activate the blower.
New ones just use a time delay on the controller board.

An interesting side note with two stage furnaces. They can generally be
set up two ways. One is really the right and best way, which is to use
two heat call wires, one for each stage. The other way is to just use
one wire and set it up so the control board makes the call based on how
long the furnace runs. So, it starts at low stage, then if it's still
running after ~ 8 mins or so, it goes to high. Obviously that's far
from ideal. If you need a bigger increase in temp, you have to wait 8 mins
for it to kick up. And it also might kick up and then shut off in a just
another short period, if the temp was almost where it needed to be.

The thermostat knows what the req increase is and can invoke high stage
at the beginning. But it takes an extra wire, that many installs probably
don't have. It also takes a two stage thermostat.
I'd also bet that a lot of furnaces are installed using the inferior
method anyway, because the installers are half-assed, don't want
to change to a two stage thermostat, etc.




I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats).

Bingo.



He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.

I agree, I'd do more investigating, starting with what the voltages are
at the inputs to the unit and at the activation terminal going to the
heat pump.

heat pumps have a lot of crazy modes for defrost etc.

does yours also have resistance coils heating?

maybe it was in another mode?

m

On Fri, 29 Nov 2019 12:00:59 -0500, Ralph Mowery
wrote:

In article ,
says...

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work. I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats). He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.



This is not a furnace, but a heat pump.

The fan on the air handler runs when it is calling for heat. It is the
out side unit that is not running. The relay for it has no voltage
going to the coil that tells it to pull in and run the compressor and
the fan for the outside coils.

The thing acts up so infrequent it is difficult for me to do much but
just want to get it started. I hate cold weather and seems like my
brain freezes up when cold. I call anyting below about 50 cold being in
the middle of NC.


The LED indicator will still be a way for a quick peek without having
to get your meter out. I would start with it on the white wire from
the thermostat inside the air handler and get that out of the picture.
The first rule of trouble shooting is "can you draw a circle around
the problem"? You want to get as much as you can outside that circle.
You already seemed to have eliminated the condenser since you don't
have the pick shot to the relay. If you eliminate the thermostat and
wiring into the air handler you are getting pretty close to that
control board. Do a visual inspection of all connections before you
buy anything.

In article ,
says...

The LED indicator will still be a way for a quick peek without having
to get your meter out. I would start with it on the white wire from
the thermostat inside the air handler and get that out of the picture.
The first rule of trouble shooting is "can you draw a circle around
the problem"? You want to get as much as you can outside that circle.
You already seemed to have eliminated the condenser since you don't
have the pick shot to the relay. If you eliminate the thermostat and
wiring into the air handler you are getting pretty close to that
control board. Do a visual inspection of all connections before you
buy anything.



One of my metrs is a Fluke T5-1000. Very handy as for checking voltages
it goes from low voltage to high voltages and auto from AC to DC. Just
slap the leads across a circuit and if any voltage from a volt or so up
to maybe 1000 they will show up.
It also does ohms and is very well protected. While at work using them,
we would go across fuses on a 240 volt circuit and if the fuse was open,
the meter took it just fine.
It will also do AC amps like the clamp on type. All this about the size
of a bannana.


My favorite for simple trouble shooting is a Fluke T2. Same size,but
has about 8 leds on it that light up on voltages of 6 volts to 600 volts
AC or DC. It will show continuenty of a circuit that has a very low
ohms in it. Just 2 wires like the led thing you are talking about, but
does much more.

I did take time today to pull the wiring diagram. If it stops on me
again, I will try to follow the 24 volt control circuit to see where it
stops. It must be in that as the relay did not have any voltage across
it that starts the compressor and outside fan. They both run if I push
the relay in with a screwdriver.

The control board is just a block with not much information on it. It
does have a trouble shooting LED, but it blinks once per second like the
paper says it should if nothing is wrong.

On Fri, 29 Nov 2019 16:50:04 -0500, Ralph Mowery
wrote:

In article ,
says...

The LED indicator will still be a way for a quick peek without having
to get your meter out. I would start with it on the white wire from
the thermostat inside the air handler and get that out of the picture.
The first rule of trouble shooting is "can you draw a circle around
the problem"? You want to get as much as you can outside that circle.
You already seemed to have eliminated the condenser since you don't
have the pick shot to the relay. If you eliminate the thermostat and
wiring into the air handler you are getting pretty close to that
control board. Do a visual inspection of all connections before you
buy anything.



One of my metrs is a Fluke T5-1000. Very handy as for checking voltages
it goes from low voltage to high voltages and auto from AC to DC. Just
slap the leads across a circuit and if any voltage from a volt or so up
to maybe 1000 they will show up.
It also does ohms and is very well protected. While at work using them,
we would go across fuses on a 240 volt circuit and if the fuse was open,
the meter took it just fine.
It will also do AC amps like the clamp on type. All this about the size
of a bannana.


My favorite for simple trouble shooting is a Fluke T2. Same size,but
has about 8 leds on it that light up on voltages of 6 volts to 600 volts
AC or DC. It will show continuenty of a circuit that has a very low
ohms in it. Just 2 wires like the led thing you are talking about, but
does much more.

I did take time today to pull the wiring diagram. If it stops on me
again, I will try to follow the 24 volt control circuit to see where it
stops. It must be in that as the relay did not have any voltage across
it that starts the compressor and outside fan. They both run if I push
the relay in with a screwdriver.

The control board is just a block with not much information on it. It
does have a trouble shooting LED, but it blinks once per second like the
paper says it should if nothing is wrong.


There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.

On Fri, 29 Nov 2019 11:02:59 -0500, Ralph Mowery
wrote:

In article ,
says...

I'd also inspect the relay on the control board that drives the compressor unit,
if possible. Maybe the relay is sticking/failing and sometimes it will not close to activate. He should also measure the voltage at the control board
that goes to the compressor when it's having the problem, see if it has
voltage or not. That would help determine if it's before that point or an
intermittent wiring problem going to the compressor unit. But it doesn't
seem like a wiring thing, since recycling the power restores normal operation.
So far, it sounds most likely a control board problem.

If it looks like that's it, he could buy a new one. If it turns out that it's
not that, very good chance he can sell it on Ebay and get most of his money
back. Very cheap compared to what it would cost to call out an HVAC guy.
the compressor.



I worked for years as an electrician and instrument person at a large
plant, so doing the actual work and measurment ( I have all kinds of
test instruments at home) is no problem. I dealt with computer controled
equipment and some 480 volt 3 phase heaters that pulled about 300 amps.
Just knowing what to look for on this simple controller is my problem.

That thing just will not stay screwed up long enough to find the
problem. It only does it a few times in the winter. Just started a year
or two ago.

I did check the relay that powers the compressor and fan. It did not
have any power going to them. Pushing it in by hand (screwdriver)
starts them.

I may buy a control board off ebay. Seems that I looked into it last
year but did not follow up when I bought a spare capacitor and relay
just so I would have them at hand.

The board would be cheap compaired to calling the man. I learned my
lesson on that a few years back when I was charged about $ 350 just to
have the capacitor replaced.
Personally "I" would start by checking ALL connections in the low
voltage control circuit. clean all contacts to "bright" and reinstall
with de-oxit or similar connection "dope". Any place with push or
slide connections, buff the contacts with a hard pink eraser. Also
trty wiggling any solid core wires to check for cracks, and check for
ANY evidence of moisture, corrosion, or buf nests.

On Fri, 29 Nov 2019 12:00:59 -0500, Ralph Mowery
wrote:

In article ,
says...

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work. I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats). He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.



This is not a furnace, but a heat pump.

The fan on the air handler runs when it is calling for heat. It is the
out side unit that is not running. The relay for it has no voltage
going to the coil that tells it to pull in and run the compressor and
the fan for the outside coils.

The thing acts up so infrequent it is difficult for me to do much but
just want to get it started. I hate cold weather and seems like my
brain freezes up when cold. I call anyting below about 50 cold being in
the middle of NC.

next time it doesn't run check for voltage out at the controller
instead of voltage in at the contactor

On Fri, 29 Nov 2019 15:23:26 -0500, wrote:

On Fri, 29 Nov 2019 12:00:59 -0500, Ralph Mowery
wrote:

In article ,
says...

The heat will not run unless the fan is on and depending on the
thermostat base, you might have to turn the fan switch on to get heat.
I am not sure about furnaces, I haven't seen one in 35 years but that
is how air handlers work. I do know you can run most heat only
furnaces on a 2 wire thermostat (just reading the instructions for
thermostats). He is definitely in the situation where poking around
with a meter (even a 24v test light) and looking at the wiring diagram
is in order. Just throwing parts at it and trying to get lucky is
silly.



This is not a furnace, but a heat pump.

The fan on the air handler runs when it is calling for heat. It is the
out side unit that is not running. The relay for it has no voltage
going to the coil that tells it to pull in and run the compressor and
the fan for the outside coils.

The thing acts up so infrequent it is difficult for me to do much but
just want to get it started. I hate cold weather and seems like my
brain freezes up when cold. I call anyting below about 50 cold being in
the middle of NC.


The LED indicator will still be a way for a quick peek without having
to get your meter out. I would start with it on the white wire from
the thermostat inside the air handler and get that out of the picture.
The first rule of trouble shooting is "can you draw a circle around
the problem"? You want to get as much as you can outside that circle.
You already seemed to have eliminated the condenser since you don't
have the pick shot to the relay. If you eliminate the thermostat and
wiring into the air handler you are getting pretty close to that
control board. Do a visual inspection of all connections before you
buy anything.
+1

On Friday, November 29, 2019 at 4:50:14 PM UTC-5, Ralph Mowery wrote:
In article ,
says...

The LED indicator will still be a way for a quick peek without having
to get your meter out. I would start with it on the white wire from
the thermostat inside the air handler and get that out of the picture.
The first rule of trouble shooting is "can you draw a circle around
the problem"? You want to get as much as you can outside that circle.
You already seemed to have eliminated the condenser since you don't
have the pick shot to the relay. If you eliminate the thermostat and
wiring into the air handler you are getting pretty close to that
control board. Do a visual inspection of all connections before you
buy anything.



One of my metrs is a Fluke T5-1000. Very handy as for checking voltages
it goes from low voltage to high voltages and auto from AC to DC. Just
slap the leads across a circuit and if any voltage from a volt or so up
to maybe 1000 they will show up.
It also does ohms and is very well protected. While at work using them,
we would go across fuses on a 240 volt circuit and if the fuse was open,
the meter took it just fine.
It will also do AC amps like the clamp on type. All this about the size
of a bannana.


My favorite for simple trouble shooting is a Fluke T2. Same size,but
has about 8 leds on it that light up on voltages of 6 volts to 600 volts
AC or DC. It will show continuenty of a circuit that has a very low
ohms in it. Just 2 wires like the led thing you are talking about, but
does much more.

I did take time today to pull the wiring diagram. If it stops on me
again, I will try to follow the 24 volt control circuit to see where it
stops.

Shouldn't even need a circuit diagram to trace the wiring. Look for the
color of wires that drive the contactor outside and look for them in the
cable coming from it to the air handler control board. Also the terminals
should be marked with something that you can decipher by looking at it.
If there is 24v there when it won't run, then wiring is the problem,
otherwise look at what's at the W terminal from the thermostat.





It must be in that as the relay did not have any voltage across
it that starts the compressor and outside fan. They both run if I push
the relay in with a screwdriver.

The control board is just a block with not much information on it. It
does have a trouble shooting LED, but it blinks once per second like the
paper says it should if nothing is wrong.

In article ,
says...

There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.



The control circuit is 24 V AC. The block diagram shows a relay contact
or two in series with the motor contactor for the compressor.

I had forgotten I had the diagram from last year when it acted up. Just
cutting it off and back on cleared the problem, so I did not go into it
last year. I had so much going on the day it quit on me this year, my
mind was on other things.

The LED has 3 or 4 flash rates to indicate a couple of problems. It
flashes normal. It may be as simple as a bad connectiion of dirt on
one of the relay contacts.

The thing quits so infrequent it is difficult to trace when other things
are going on.

Often in simple circuits (and more complicated ones) a product will have
several known faults that hapen 90 % or more of the time. I just though
someone may have ran into it before.

On Fri, 29 Nov 2019 18:56:50 -0500, Ralph Mowery
wrote:

In article ,
says...

There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.



The control circuit is 24 V AC. The block diagram shows a relay contact
or two in series with the motor contactor for the compressor.

I had forgotten I had the diagram from last year when it acted up. Just
cutting it off and back on cleared the problem, so I did not go into it
last year. I had so much going on the day it quit on me this year, my
mind was on other things.

The LED has 3 or 4 flash rates to indicate a couple of problems. It
flashes normal. It may be as simple as a bad connectiion of dirt on
one of the relay contacts.

The thing quits so infrequent it is difficult to trace when other things
are going on.

Often in simple circuits (and more complicated ones) a product will have
several known faults that hapen 90 % or more of the time. I just though
someone may have ran into it before.

You are right, mass production means mass failures if there is a flaw
in the process. In my biz, every machine usually only had a few things
that went wrong. If you could identify the flaw and come up with a fix
in the process, there was money to be had.

On 11/29/2019 6:56 PM, Ralph Mowery wrote:
In article ,
says...
There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.


The control circuit is 24 V AC. The block diagram shows a relay contact
or two in series with the motor contactor for the compressor.

I had forgotten I had the diagram from last year when it acted up. Just
cutting it off and back on cleared the problem, so I did not go into it
last year. I had so much going on the day it quit on me this year, my
mind was on other things.

The LED has 3 or 4 flash rates to indicate a couple of problems. It
flashes normal. It may be as simple as a bad connectiion of dirt on
one of the relay contacts.

The thing quits so infrequent it is difficult to trace when other things
are going on.

Often in simple circuits (and more complicated ones) a product will have
several known faults that hapen 90 % or more of the time. I just though
someone may have ran into it before.

Check for loose or corroded terminal connections.

On Friday, November 29, 2019 at 8:16:08 PM UTC-5, wrote:
On Fri, 29 Nov 2019 18:56:50 -0500, Ralph Mowery
wrote:

In article ,
says...

There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.



The control circuit is 24 V AC. The block diagram shows a relay contact
or two in series with the motor contactor for the compressor.

I had forgotten I had the diagram from last year when it acted up. Just
cutting it off and back on cleared the problem, so I did not go into it
last year. I had so much going on the day it quit on me this year, my
mind was on other things.

The LED has 3 or 4 flash rates to indicate a couple of problems. It
flashes normal. It may be as simple as a bad connectiion of dirt on
one of the relay contacts.

The thing quits so infrequent it is difficult to trace when other things
are going on.

Often in simple circuits (and more complicated ones) a product will have
several known faults that hapen 90 % or more of the time. I just though
someone may have ran into it before.

You are right, mass production means mass failures if there is a flaw
in the process. In my biz, every machine usually only had a few things
that went wrong. If you could identify the flaw and come up with a fix
in the process, there was money to be had.

The people who work for me fall into couple of groups on troubleshooting.

One is in the camp of: It's a brand XXX model 123 so it's always a faulty output relay. They're right a lot of the time and that reinforces the approach. When it's wrong they're lost.

Another is: Gather all the data, check everything, avoid a diagnosis until the last moment. These guys are slow but get it right. I've maybe got one like that.

The most common though is to make the diagnosis too soon and then exclude all data that doesn't confirm it. I try to keep these guys away from expensive equipment but there's no way to fix their approach. It's not that they ignore conflicting data, they can't actually see it.

In article ,
says...

The people who work for me fall into couple of groups on troubleshooting.

One is in the camp of: It's a brand XXX model 123 so it's always a faulty output relay. They're right a lot of the time and that reinforces the approach. When it's wrong they're lost.

Another is: Gather all the data, check everything, avoid a diagnosis until the last moment. These guys are slow but get it right. I've maybe got one like that.

The most common though is to make the diagnosis too soon and then exclude all data that doesn't confirm it. I try to keep these guys away from expensive equipment but there's no way to fix their approach. It's not that they ignore conflicting data, they can't actually see it.



I like to think that I fall in the middle of that.

When working on equipment, about 90% of the time it will be the same
part that fails. For example at work there was a piece of equipment
that had a relay in it that often failed. It just plugged in.
Instead of taking time to think about it, I would put in a new relay.
Takes about 10 seconds. If that failed to fix the problem, then out
comes the test equipment and circuit diagrams to do the trouble
shooting.

On Sun, 1 Dec 2019 05:43:01 -0800 (PST), TimR
wrote:

On Friday, November 29, 2019 at 8:16:08 PM UTC-5, wrote:
On Fri, 29 Nov 2019 18:56:50 -0500, Ralph Mowery
wrote:

In article ,
says...

There must be a processor on that card. If the thermostat wires go
right to the card and the connections are good you really only have
the output to the relay. Maybe the driver transistor/Triac is bad. It
might also look at the card to see if there is a flaky land pattern or
a cold solder joint. Is this AC to the relay or DC? Typically HVAC is
AC but I wouldn't be surprised that these CPU controlled ones use DC.
If it is AC, you also have the connection from the AC supply into the
card.
The LED is really just the "heartbeat" indicating the processor is
running.



The control circuit is 24 V AC. The block diagram shows a relay contact
or two in series with the motor contactor for the compressor.

I had forgotten I had the diagram from last year when it acted up. Just
cutting it off and back on cleared the problem, so I did not go into it
last year. I had so much going on the day it quit on me this year, my
mind was on other things.

The LED has 3 or 4 flash rates to indicate a couple of problems. It
flashes normal. It may be as simple as a bad connectiion of dirt on
one of the relay contacts.

The thing quits so infrequent it is difficult to trace when other things
are going on.

Often in simple circuits (and more complicated ones) a product will have
several known faults that hapen 90 % or more of the time. I just though
someone may have ran into it before.

You are right, mass production means mass failures if there is a flaw
in the process. In my biz, every machine usually only had a few things
that went wrong. If you could identify the flaw and come up with a fix
in the process, there was money to be had.

The people who work for me fall into couple of groups on troubleshooting.

One is in the camp of: It's a brand XXX model 123 so it's always a faulty output relay. They're right a lot of the time and that reinforces the approach. When it's wrong they're lost.

Another is: Gather all the data, check everything, avoid a diagnosis until the last moment. These guys are slow but get it right. I've maybe got one like that.

The most common though is to make the diagnosis too soon and then exclude all data that doesn't confirm it. I try to keep these guys away from expensive equipment but there's no way to fix their approach. It's not that they ignore conflicting data, they can't actually see it.
There's one other type, and they are the most irritating.
The ones that got lucky once and doing "X" fixed it -so that's always
the problem - - - Can't tell them anything - can't teach them
anything - particularly when what they decided was the solution to the
problem was "replace everything" - with a different part.

On Sun, 1 Dec 2019 10:27:39 -0500, Ralph Mowery
wrote:

In article ,
says...

The people who work for me fall into couple of groups on troubleshooting.

One is in the camp of: It's a brand XXX model 123 so it's always a faulty output relay. They're right a lot of the time and that reinforces the approach. When it's wrong they're lost.

Another is: Gather all the data, check everything, avoid a diagnosis until the last moment. These guys are slow but get it right. I've maybe got one like that.

The most common though is to make the diagnosis too soon and then exclude all data that doesn't confirm it. I try to keep these guys away from expensive equipment but there's no way to fix their approach. It's not that they ignore conflicting data, they can't actually see it.



I like to think that I fall in the middle of that.

When working on equipment, about 90% of the time it will be the same
part that fails. For example at work there was a piece of equipment
that had a relay in it that often failed. It just plugged in.
Instead of taking time to think about it, I would put in a new relay.
Takes about 10 seconds. If that failed to fix the problem, then out
comes the test equipment and circuit diagrams to do the trouble
shooting.


I do similar - but usually I "test" the relay (or whatever) to either
prove it IS the problem or it IS NOT the problem. This is because I
don't always have the replacement part available, and in most cases if
I get the part and it is NOT the problem it is not returnable - and
I'm stuck with it. If IDO have a "Known Good" part to swap in, it IS
(generally) the quickest way to prove the fault.

In article ,
says...

I do similar - but usually I "test" the relay (or whatever) to either
prove it IS the problem or it IS NOT the problem. This is because I
don't always have the replacement part available, and in most cases if
I get the part and it is NOT the problem it is not returnable - and
I'm stuck with it. If IDO have a "Known Good" part to swap in, it IS
(generally) the quickest way to prove the fault.



If I had to buy a part, I would try to make sure it really was bad.
Where I worked, we had thousnds of spare parts as the plant needed to
run 24 hours a day, nonstop. Usualy had one or more replacements for
most everything. Those were small realys and I would usually put one in
my pocket before I left the shop as it was in another building. I also
carried some test equipment just in the rare case it was not that part.
There was another part that was known to fail so took one of those with
me, but as it took about 20 minuits to change it out, I would run a few
tests to determin if it was the problem.

I did have a Toyota that started running rough. As I am not a very good
car mechanic, I threw a few logical inexpensive parts at it. Plugs,
wires and coil. The hint page on Autozone pointed to a mass air flow
sensor, but it was around $ 500. Took it to the Toyota dealer thinking
they could test it. Two weeks or more later they finally decided it was
the sensor and put in a new one. Not sure what kind of mechanic they
had, but did not seem to be much of one.

Then there are the ones that do not have a clue and do not seem to know
what to do, so they just change parts blindly.

On Sun, 01 Dec 2019 14:39:19 -0500, Clare Snyder
wrote:

On Sun, 1 Dec 2019 10:27:39 -0500, Ralph Mowery
wrote:

In article ,
says...

The people who work for me fall into couple of groups on troubleshooting.

One is in the camp of: It's a brand XXX model 123 so it's always a faulty output relay. They're right a lot of the time and that reinforces the approach. When it's wrong they're lost.

Another is: Gather all the data, check everything, avoid a diagnosis until the last moment. These guys are slow but get it right. I've maybe got one like that.

The most common though is to make the diagnosis too soon and then exclude all data that doesn't confirm it. I try to keep these guys away from expensive equipment but there's no way to fix their approach. It's not that they ignore conflicting data, they can't actually see it.



I like to think that I fall in the middle of that.

When working on equipment, about 90% of the time it will be the same
part that fails. For example at work there was a piece of equipment
that had a relay in it that often failed. It just plugged in.
Instead of taking time to think about it, I would put in a new relay.
Takes about 10 seconds. If that failed to fix the problem, then out
comes the test equipment and circuit diagrams to do the trouble
shooting.


I do similar - but usually I "test" the relay (or whatever) to either
prove it IS the problem or it IS NOT the problem. This is because I
don't always have the replacement part available, and in most cases if
I get the part and it is NOT the problem it is not returnable - and
I'm stuck with it. If IDO have a "Known Good" part to swap in, it IS
(generally) the quickest way to prove the fault.

Goes a lot faster if you know what to test first. The best test is to
plug in the good one you have in your pocket. ;-)
I have worked on all sorts of machines and some you really needed to
diagnose (like a CPU with 1000 cards in it or a check sorter with
10,000 moving parts). Since the 90s, just replacing the bad part based
on a few symptoms, is not an unreasonable approach. When I left in
1996, IBM pretty much said take a scope with you, take two, we don't
need them anymore. (along with a trunk full of other test equipment).
They didn't need me either. Any dweeb can work on a box with a half
dozen FRUs, functionally packaged.

On Sun, 1 Dec 2019 15:24:46 -0500, Ralph Mowery
wrote:

In article ,
says...

I do similar - but usually I "test" the relay (or whatever) to either
prove it IS the problem or it IS NOT the problem. This is because I
don't always have the replacement part available, and in most cases if
I get the part and it is NOT the problem it is not returnable - and
I'm stuck with it. If IDO have a "Known Good" part to swap in, it IS
(generally) the quickest way to prove the fault.



If I had to buy a part, I would try to make sure it really was bad.
Where I worked, we had thousnds of spare parts as the plant needed to
run 24 hours a day, nonstop. Usualy had one or more replacements for
most everything. Those were small realys and I would usually put one in
my pocket before I left the shop as it was in another building. I also
carried some test equipment just in the rare case it was not that part.
There was another part that was known to fail so took one of those with
me, but as it took about 20 minuits to change it out, I would run a few
tests to determin if it was the problem.

I did have a Toyota that started running rough. As I am not a very good
car mechanic, I threw a few logical inexpensive parts at it. Plugs,
wires and coil. The hint page on Autozone pointed to a mass air flow
sensor, but it was around $ 500. Took it to the Toyota dealer thinking
they could test it. Two weeks or more later they finally decided it was
the sensor and put in a new one. Not sure what kind of mechanic they
had, but did not seem to be much of one.

Then there are the ones that do not have a clue and do not seem to know
what to do, so they just change parts blindly.
The MAF on the 22RE and 4MGE as well as many others was actually
REALLY easy to test with an ohm-meter and your finger.(I was Toyota
service manager for 10 years from '79 to '89 and toyota tech back in
'72

On Sunday, December 1, 2019 at 3:24:57 PM UTC-5, Ralph Mowery wrote:
In article ,
says...

I do similar - but usually I "test" the relay (or whatever) to either
prove it IS the problem or it IS NOT the problem. This is because I
don't always have the replacement part available, and in most cases if
I get the part and it is NOT the problem it is not returnable - and
I'm stuck with it. If IDO have a "Known Good" part to swap in, it IS
(generally) the quickest way to prove the fault.



If I had to buy a part, I would try to make sure it really was bad.
Where I worked, we had thousnds of spare parts as the plant needed to
run 24 hours a day, nonstop. Usualy had one or more replacements for
most everything. Those were small realys and I would usually put one in
my pocket before I left the shop as it was in another building. I also
carried some test equipment just in the rare case it was not that part.
There was another part that was known to fail so took one of those with
me, but as it took about 20 minuits to change it out, I would run a few
tests to determin if it was the problem.

I did have a Toyota that started running rough. As I am not a very good
car mechanic, I threw a few logical inexpensive parts at it. Plugs,
wires and coil. The hint page on Autozone pointed to a mass air flow
sensor, but it was around $ 500. Took it to the Toyota dealer thinking
they could test it. Two weeks or more later they finally decided it was
the sensor and put in a new one. Not sure what kind of mechanic they
had, but did not seem to be much of one.

Then there are the ones that do not have a clue and do not seem to know
what to do, so they just change parts blindly.

The onboard diagnostics and code setting could be better too. I posted
the other thread about the BMW X5 having issues and then suddenly not
running at all. As I said there, it was the intake plumbing coming
apart just after the MAF. I spotted it visually. But before resetting
all the codes, I decided to read them out just to see what was set.
I made a bet with myself that MAF problem would not be one of them.
I was right. It had lean codes set, misfire set, idle air valve
not working...... No MAF codes.

You'd think with little air moving through the MAF it would say something
like MAF output low or inconsistent. Or MAF output implausible.
Those Germans like implausible. For example if the brake light sensor
is bad, it will say Implausible - Simultaneous brake and throttle.
But you have the engine running, albeit poorly, at 3000 RPMs with
most of the air not registering through the MAF, and no MAF codes.