Troubleshooting advice requested, because the LED blinking
constantly supposedly indicates that the heater is wired
in reverse (which really isn't very likely, so I must be
misinterpreting something obvious).

Heater worked last year (AFAIK).

It just started getting cold in California, so, the heater power
was turned on, and ... and ... and ... uh ... um ... no heat.
https://c4.staticflickr.com/8/7508/1...4311f464_k.jpg

Thermostat batteries are good:
https://c1.staticflickr.com/9/8595/1...3c98abbd_k.jpg

Heater power is on and the blower blows but the red led blinks
at a steady pace forever.
https://c4.staticflickr.com/8/7513/1...4a54e186_c.jpg

Checked that the switches inside were all on:
https://c4.staticflickr.com/8/7510/1...c399d625_b.jpg

Checked that the fuse on the circuit board was good:
https://c1.staticflickr.com/9/8672/1...4a6d21f8_c.jpg

The sticker says constant flashes indicates reverse wiring:
https://c4.staticflickr.com/8/7505/1...4f42e6c5_c.jpg

But, there's no way the wiring was changed between last year & now.
https://c4.staticflickr.com/8/7540/1...2d8775fe_c.jpg

Here's what it looks like inside:
https://c4.staticflickr.com/8/7561/1...7f78bee3_b.jpg
https://c1.staticflickr.com/9/8561/1...7cc1f787_b.jpg

I don't know where the model number is, so, I don't have a manual
yet.

Debugging suggestions are requested, and very helpful. Thanks!

On 12/19/2014 6:56 PM, Danny D. wrote:
Troubleshooting advice requested, because the LED blinking
constantly supposedly indicates that the heater is wired
in reverse (which really isn't very likely, so I must be
misinterpreting something obvious).

Heater worked last year (AFAIK).

It just started getting cold in California, so, the heater power
was turned on, and ... and ... and ... uh ... um ... no heat.
https://c4.staticflickr.com/8/7508/1...4311f464_k.jpg

Thermostat batteries are good:
https://c1.staticflickr.com/9/8595/1...3c98abbd_k.jpg

Heater power is on and the blower blows but the red led blinks
at a steady pace forever.
https://c4.staticflickr.com/8/7513/1...4a54e186_c.jpg

Checked that the switches inside were all on:
https://c4.staticflickr.com/8/7510/1...c399d625_b.jpg

Checked that the fuse on the circuit board was good:
https://c1.staticflickr.com/9/8672/1...4a6d21f8_c.jpg

The sticker says constant flashes indicates reverse wiring:
https://c4.staticflickr.com/8/7505/1...4f42e6c5_c.jpg

But, there's no way the wiring was changed between last year & now.
https://c4.staticflickr.com/8/7540/1...2d8775fe_c.jpg

Here's what it looks like inside:
https://c4.staticflickr.com/8/7561/1...7f78bee3_b.jpg
https://c1.staticflickr.com/9/8561/1...7cc1f787_b.jpg

I don't know where the model number is, so, I don't have a manual
yet.

Debugging suggestions are requested, and very helpful. Thanks!


Model number inside the case, in your machine
probably on the inner ceiling. As to reverse
polarity, you'd have to use a VOM to confirm
the black is hot, white is neutral.

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

Stormin Mormon wrote, on Fri, 19 Dec 2014 19:13:20 -0500:

Model number inside the case, in your machine
probably on the inner ceiling. As to reverse
polarity, you'd have to use a VOM to confirm
the black is hot, white is neutral.

Thanks for that advice.

I can check the polarity, but, really, there's no way
it changed.

So, I must be interpreting the flashes incorrectly.

Here is the full-size secret decoder ring:
https://c4.staticflickr.com/8/7484/1...5d624fe0_c.jpg

Given that, what do folks make of these flashes in
this 30-second video while the cover was still on the unit?
https://www.flickr.com/photos/98287134@N02/16060716735/

On Friday, December 19, 2014 6:57:23 PM UTC-5, Danny D. wrote:
Troubleshooting advice requested, because the LED blinking
constantly supposedly indicates that the heater is wired
in reverse (which really isn't very likely, so I must be
misinterpreting something obvious).

Heater worked last year (AFAIK).

It just started getting cold in California, so, the heater power
was turned on, and ... and ... and ... uh ... um ... no heat.
https://c4.staticflickr.com/8/7508/1...4311f464_k.jpg

Thermostat batteries are good:
https://c1.staticflickr.com/9/8595/1...3c98abbd_k.jpg

Heater power is on and the blower blows but the red led blinks
at a steady pace forever.
https://c4.staticflickr.com/8/7513/1...4a54e186_c.jpg

Checked that the switches inside were all on:
https://c4.staticflickr.com/8/7510/1...c399d625_b.jpg

Checked that the fuse on the circuit board was good:
https://c1.staticflickr.com/9/8672/1...4a6d21f8_c.jpg

The sticker says constant flashes indicates reverse wiring:
https://c4.staticflickr.com/8/7505/1...4f42e6c5_c.jpg

But, there's no way the wiring was changed between last year & now.
https://c4.staticflickr.com/8/7540/1...2d8775fe_c.jpg

Here's what it looks like inside:
https://c4.staticflickr.com/8/7561/1...7f78bee3_b.jpg
https://c1.staticflickr.com/9/8561/1...7cc1f787_b.jpg

I don't know where the model number is, so, I don't have a manual
yet.

Debugging suggestions are requested, and very helpful. Thanks!

According to that secret decoder table, it tells you what's wrong
by blinking short blinks, followed by long blinks. Those continue
indefinitely, in a pattern. So, are you saying it's not doing that,
but instead it's giving you no pattern, just rapid flashes, which
the table says is reversed polarity?

If so, best guess would be that the oontroller board is kaput. Did you
have that flakey generator running it?

trader_4 wrote, on Fri, 19 Dec 2014 16:14:54 -0800:

According to that secret decoder table, it tells you what's wrong
by blinking short blinks, followed by long blinks. Those continue
indefinitely, in a pattern. So, are you saying it's not doing that,
but instead it's giving you no pattern, just rapid flashes, which
the table says is reversed polarity?

Here is exactly what the blinking is doing with the cover off
and me pressing on the door switch manually:
https://www.flickr.com/photos/98287134@N02/15438398234/

This is the secret decoder ring in a full-size JPEG file:
https://c4.staticflickr.com/8/7484/1...5d624fe0_c.jpg

What do you make of those blinks with the cover off the unit?

On 12/19/2014 10:21 PM, Danny D. wrote:

Here is exactly what the blinking is doing with the cover off
and me pressing on the door switch manually:
https://www.flickr.com/photos/98287134@N02/15438398234/

This is the secret decoder ring in a full-size JPEG file:
https://c4.staticflickr.com/8/7484/1...5d624fe0_c.jpg

What do you make of those blinks with the cover off the unit?

I could not tell if it was continuous, or blinking 11.

In any case, and open ground can some times
give a fault code. I'd get out the VOM, and
check for polarity and also check for open
ground.

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

Stormin Mormon wrote, on Sat, 20 Dec 2014 06:01:41 -0500:

I could not tell if it was continuous, or blinking 11.

If it's 11, then that corresponds to the following (which I don't
understand).
11: NO PREVIOUS CODE - Stored status codes are erased when power
(115V or 24V) to control is interrupted or 48 hours after each
fault is cleared

What does that mean?

On 12/20/2014 7:51 AM, Danny D. wrote:
Stormin Mormon wrote, on Sat, 20 Dec 2014 06:01:41 -0500:

I could not tell if it was continuous, or blinking 11.

If it's 11, then that corresponds to the following (which I don't
understand).
11: NO PREVIOUS CODE - Stored status codes are erased when power
(115V or 24V) to control is interrupted or 48 hours after each
fault is cleared

What does that mean?

Means that either someone turned off the power
(so the unit lost its memory kind of like a VCR
blinking 12:00) or that the fault was so long
ago, that the unit lost its memory.

In any case, please try shutting off the power
for 30 seconds or so, and turn it back on. Some
times that handles nussiance trips.

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

Stormin Mormon wrote, on Sat, 20 Dec 2014 06:01:41 -0500:

I could not tell if it was continuous, or blinking 11.

If it's continuous, that corresponds to:
RAPID FLASHING - Line voltage (115V) polarity reversed.
If twinned, refer to twinning kit instructions.

What does "twinned" mean?

On Saturday, December 20, 2014 6:01:47 AM UTC-5, Stormin Mormon wrote:
On 12/19/2014 10:21 PM, Danny D. wrote:

Here is exactly what the blinking is doing with the cover off
and me pressing on the door switch manually:
https://www.flickr.com/photos/98287134@N02/15438398234/

This is the secret decoder ring in a full-size JPEG file:
https://c4.staticflickr.com/8/7484/1...5d624fe0_c.jpg

What do you make of those blinks with the cover off the unit?

I could not tell if it was continuous, or blinking 11.

In any case, and open ground can some times
give a fault code. I'd get out the VOM, and
check for polarity and also check for open
ground.


The video wouldn't play in Internet Explorer, just sound. In Chrome
it played for me and clearly it shows 1 long flash, 5 short flashes,
followed by continuous flashes. The other video, with the door on,
just shows it flashing continously, no patterm.

Two problems. First the table says the codes are given by the number
of long flashes and short flashes, which would lead you to believe
the long flashes should come first, not the other way around.

Second, no matter, there is no table entry for 1-5 or 5-1.

The continous flashing with the cover on, in the other video, I would
agree looks like line polarity reversed. Which for a previously installed
furnace would appear to be virtually impossible. Another possibility
would be that the control board was replaced previously with a different
type that has different codes.

So, I agree, I'd check with a VOM to make sure AC is in order. After
that, IDK. We don't know the sequence of what comes before those videos.
If the furnace winds up with that constant blinking in the first video
right after power has been removed, then turned back on, I'd say it's
most likely the control board. If the light is just on steady, which I
think is normal condition, and then when it goes to *fire*, he gets the
1 -5 sequence, then I'd say it's more likely something else, ie that it's
detecting something wrong, like pressure, when purging. But why it's not
in the list, the blinks seem backward, I guess that's just par for the
course with the stuff at D's house.

trader_4 wrote, on Sat, 20 Dec 2014 05:19:01 -0800:

The video wouldn't play in Internet Explorer, just sound. In Chrome
it played for me and clearly it shows 1 long flash, 5 short flashes,
followed by continuous flashes. The other video, with the door on,
just shows it flashing continously, no patterm.

Thanks for taking a look at it, because I saw exactly the same thing.

The video with the door on was taken after it was running for ten or
fifteen minutes, but with no heat, so I crawled into the crawlspace
where the heater was and taped the flashing.

There was nothing whatsoever done with the line voltage of this
furnace, at least not on purpose. No electricians came to the house.
And nothing was done on the furnace whatsoever.

So, for the line voltage to reverse, that would be odd.

Two problems. First the table says the codes are given by the number
of long flashes and short flashes, which would lead you to believe
the long flashes should come first, not the other way around.

I can't tell if the continuous flashes are long or short.

Second, no matter, there is no table entry for 1-5 or 5-1.

I did see, as you saw, that the first few seconds of flashes
were not the same as the rest of the flashes. I didn't know what
to make of it, but you discerned a 1-5, which makes your timing
better than mine.

Another possibility would be that the control board was replaced
previously with a different type that has different codes.

Ah. I understand what you're saying. If the control board doesn't
match the cover secret decoder ring, then that might explain a lot.

We don't know the sequence of what comes before those videos.

I'll snap a new "reboot" video today, with the power turned off to
the furnace, for a few hours, and then turned back on and started
right up so we get the "initial" sequence of flashes.

Danny D. wrote:
trader_4 wrote, on Fri, 19 Dec 2014 16:14:54 -0800:

According to that secret decoder table, it tells you what's wrong
by blinking short blinks, followed by long blinks. Those continue
indefinitely, in a pattern. So, are you saying it's not doing that,
but instead it's giving you no pattern, just rapid flashes, which
the table says is reversed polarity?

Here is exactly what the blinking is doing with the cover off
and me pressing on the door switch manually:
https://www.flickr.com/photos/98287134@N02/15438398234/

This is the secret decoder ring in a full-size JPEG file:
https://c4.staticflickr.com/8/7484/1...5d624fe0_c.jpg

What do you make of those blinks with the cover off the unit?

Hi,
I believe it is code 33. I am pretty sure.

Tony Hwang wrote, on Sat, 20 Dec 2014 19:41:51 -0700:

I believe it is code 33. I am pretty sure.

Thanks for looking as it's really hard to tell what the
blinking indicates.

If it's 33, then that corresponds to:

LIMIT OR FLAME ROLL-OUT SWITCH IS OPEN-
If open longer than three minutes, code changes to #13.
Check for:
- Defective blower motor or start capacitor
- Loose blower wheel
- Inadequate combustion air supply flame roll-out switch or fuse link
- Open flame roll-out switch, or fuse link. Manual reset or replace.
- Dirty filter or restricted duct system
- Defective switch or connections

I'm not sure I understand all of those, but some are easy,
e.g., I'll look for whereever the filter is (which has never
been cleaned to my knowledge).

Some of these controllers sense the small electrical conductivity of a fire as a flame sensor. Since the fire is grounded, the flame sense ciccuot senses to earth ground. To do that, the conntroller needs a good earth ground and it gets that through the ac connection. All 3 wires of the ac connection have to be correct. The black has to be hot. The white neutral and the green or bare ground. Check that these 3 connections are correct, including the ground connection. Also chech that these is no sign of water on the electronics. Also chcck the flame sensorrobe wire is not shorted or has water.

Mark

On 12/21/2014 2:51 AM, Danny D. wrote:
Tony Hwang wrote, on Sat, 20 Dec 2014 19:41:51 -0700:

I believe it is code 33. I am pretty sure.

Thanks for looking as it's really hard to tell what the
blinking indicates.

If it's 33, then that corresponds to:

LIMIT OR FLAME ROLL-OUT SWITCH IS OPEN-
If open longer than three minutes, code changes to #13.
Check for:
- Defective blower motor or start capacitor
- Loose blower wheel
- Inadequate combustion air supply flame roll-out switch or fuse link
- Open flame roll-out switch, or fuse link. Manual reset or replace.
- Dirty filter or restricted duct system
- Defective switch or connections

I'm not sure I understand all of those, but some are easy,
e.g., I'll look for whereever the filter is (which has never
been cleaned to my knowledge).


If this is the trouble code, you most likely have
not enough air flow through the furnace, and the
furnace is over heating. You might also have a
clogged flue.

First step is to seek for the air filter, and replace
it. Also see if the blower wheel spins while the furnace
is on, and calling for heat.

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

Tony Hwang wrote, on Sat, 20 Dec 2014 19:41:51 -0700:

I believe it is code 33. I am pretty sure.

I found where to get manuals but I can't find the exact model:
http://www.bryant.com/apps/finddocs/form.jsp?b=b

The model is a Bryant 373LAV024070 (AGJA).
https://c4.staticflickr.com/8/7568/1...8fa24051_b.jpg

The closest Bryant PDF manual I can find is:
373LAV 376CAV Downflow/Horizontal and 383KAV 395CAV Upflow Gas Furnace
http://dms.hvacpartners.com//docs/10...0B/OM04-35.pdf

383KAV Upflow Gas Furnace 373LAV Downflow Horizontal Gas Furnace
http://dms.hvacpartners.com//docs/10...83_373-005.pdf

I'll call Bryant on Monday to figure out why I can't find the
exact model in the lists of documents:
800-428-4326 from 5:00am-2:00pm (Pacific) weekdays.

You have the model. The last numbers are the specific size and output. 24 may be width, 70k btus?

Danny D. wrote, on Fri, 19 Dec 2014 23:56:58 +0000:

Debugging suggestions are requested, and very helpful. Thanks!

Here's where the Bryant 373LAV horizontal furnace stands tonight.

Blower starts, inducer motor starts, igniter starts, flame starts,
flame shuts down. Three times the igniter ignites the flame but
three times, the flame shuts down within seconds.

All the while it displays code #34.
At the end of the sequence, it shuts down and displays code #14.

Video:
https://www.flickr.com/photos/98287134@N02/15464227533/

Schematic:
https://www.flickr.com/photos/98287134@N02/15460746143/

Codes:
https://www.flickr.com/photos/98287134@N02/16083106532/

34 IGNITION PROVING FAILURE
- Control will try three more times before a lockout #14 occurs.
If flame signal lost after trial for ignition period, blower will
come on for 90 second recycle delay. Check for:
- Oxide buildup on flame sensor (clean with fine sandpaper).
- Proper flame sense microamps (.5 microamps D.C. minimum).
- Gas valve turned off. - Manual shut-off valve. - Low inlet gas pressure.
- Green wire MUST be connected to furnace sheet metal.
- Inadequate flame carryover or rough ignition.

14 IGNITION LOCKOUT
- Control will auto-reset after three hours.
Refer to #34.

On Monday, December 22, 2014 8:52:22 PM UTC-5, Danny D. wrote:
Danny D. wrote, on Fri, 19 Dec 2014 23:56:58 +0000:

Debugging suggestions are requested, and very helpful. Thanks!

Here's where the Bryant 373LAV horizontal furnace stands tonight.

Blower starts, inducer motor starts, igniter starts, flame starts,
flame shuts down. Three times the igniter ignites the flame but
three times, the flame shuts down within seconds.

All the while it displays code #34.
At the end of the sequence, it shuts down and displays code #14.

Video:
https://www.flickr.com/photos/98287134@N02/15464227533/

Schematic:
https://www.flickr.com/photos/98287134@N02/15460746143/

Codes:
https://www.flickr.com/photos/98287134@N02/16083106532/

34 IGNITION PROVING FAILURE
- Control will try three more times before a lockout #14 occurs.
If flame signal lost after trial for ignition period, blower will
come on for 90 second recycle delay. Check for:
- Oxide buildup on flame sensor (clean with fine sandpaper).
- Proper flame sense microamps (.5 microamps D.C. minimum).
- Gas valve turned off. - Manual shut-off valve. - Low inlet gas pressure.
- Green wire MUST be connected to furnace sheet metal.
- Inadequate flame carryover or rough ignition.

14 IGNITION LOCKOUT
- Control will auto-reset after three hours.
Refer to #34.

Ok, so now the question that might shed some light on what's going on
is, what changed that allowed the furnace to get this far? Previously,
it would come up with a flashing LED trouble indication as soon as power
was put on, without firing at all. Now, it's firing, then shutting down
because it thinks it hasn't lit.

I think that may be relevant, because initially you had continous LED
flashes that the chart says corresponds to reversed polarity. While
the polarity isn't reveresed, I wonder if it will also give that code
if the ground is missing? I ask that because the flame sensor is
single wire and depends on a ground path back to the controller board.
Is it possible there is a bad ground connection between the controller
board and the furnace metal?

Other than that, the most obvious and direct possibility is that the
flame sensor is bad. If you'd had this code, this behavior from the
beginning, that would be the logical place to start. But what's odd
is how it behaved very differently initially, unless that was something
to do with you having the safety switch open, how you were starting it,
etc.

trader_4 wrote, on Tue, 23 Dec 2014 04:44:15 -0800:

Ok, so now the question that might shed some light on what's going on
is, what changed that allowed the furnace to get this far? Previously,
it would come up with a flashing LED trouble indication as soon as power
was put on, without firing at all. Now, it's firing, then shutting down
because it thinks it hasn't lit.

I agree with you.

The manual says:
"NOTE: If the polarity is not correct, the STATUS LED on the
control center will flash rapidly and prevent the furnace from
heating. The control system also requires an earth ground for
proper operation of the control and flame sensing."

So, *both* the old and new LED indications point to a suspected
lack of "earth" ground (among other things).

Plus, the constant flashing stopped just about when I started testing
the power connections (although, I didn't *change* anything). I
wiggled everything. But I left the wiring as it was before.

Yet, suddenly, it stopped flashing constantly, and, instead, the
error migrated from a power problem to short cycling (which now
implicates either the flame sensor or the flame sensor control
circuit).

Yet, the flame sensor has only one wire, so, ground is clearly
the case.

I think that may be relevant, because initially you had continous LED
flashes that the chart says corresponds to reversed polarity. While the
polarity isn't reveresed, I wonder if it will also give that code if the
ground is missing? I ask that because the flame sensor is single wire
and depends on a ground path back to the controller board. Is it
possible there is a bad ground connection between the controller board
and the furnace metal?

I'm thinking the same thing. A bad ground could cause the flame proving
electrode not to have its requisite 5 microamps to 6 microamps. In the
schematic, there are two "Note #5" comments, each next to the "GV" which
is the gas valve

Note #5 says:
"5. This wire must be connected to furnace sheetmetal for control
to detect flame."
https://www.flickr.com/photos/98287134@N02/15460746143/

I'll need to check that, remove it, sand it, clean it, & re-test.

I suspect ground is critical for the flame-sensing circuit, because
the DC current is only 5 or 6 microamperes, which is so low, I'm
going to have to figure out *how* to test it using coils of wire
wrapped around an ammeter.

Other than that, the most obvious and direct possibility is that the
flame sensor is bad. If you'd had this code, this behavior from the
beginning, that would be the logical place to start. But what's odd is
how it behaved very differently initially, unless that was something to
do with you having the safety switch open, how you were starting it,
etc.

Looking at the troubleshooting flow chart, it does now imply that
either the flame proving electrode is bad, or that the control to
that flame sensor is bad.
https://www.flickr.com/photos/98287134@N02/15894320489/

I agree with you:
1. Today I will clean all the grounds.
2. I will check that "Note #5" wire listed in the schematic.
3. I will re-clean the flame sensing electrode (just in case).
4. I will figure out how to measure 5 or 6 microamperes
(and it can be as low as half a microampere).

Danny D. wrote, on Tue, 23 Dec 2014 13:21:56 +0000:

So, *both* the old and new LED indications point to a suspected lack of
"earth" ground (among other things).

Found a service manual online, by the way:
http://manualslib.com/manual/22390/B...es-373lav.html

Danny D. wrote, on Tue, 23 Dec 2014 14:36:38 +0000:

Found a service manual online, by the way:
http://manualslib.com/manual/22390/B...es-373lav.html

Here's a better link to the service manual so you can
see the schematic and troubleshooting flowchart:
http://dms.hvacpartners.com/docs/100...00/SP04-62.pdf

On Tuesday, December 23, 2014 9:37:04 AM UTC-5, Danny D. wrote:
Danny D. wrote, on Tue, 23 Dec 2014 13:21:56 +0000:

So, *both* the old and new LED indications point to a suspected lack of
"earth" ground (among other things).


If the ground is affecting the flame sensor, then it't the ground path
from the metal cabinet/frame of the furnace to the control board. That's
where I'd be looking. There must be a ground wire that goes from the control
board to the frame and the frame is also grounded to the incoming AC.

Danny D. wrote, on Fri, 19 Dec 2014 23:56:58 +0000:

It just started getting cold in California, so, the heater power
was turned on, and ... and ... and ... uh ... um ... no heat.
https://c4.staticflickr.com/8/7508/1...4311f464_k.jpg

Update!

The heater certainly hasn't been turned on in a year, and maybe
in two years (as last year was warm). I don't remember, but, anyway,
the problem first looked like a reverse wire but the code was
basically constantly blinking.

As far as I can tell, that just means whatever old code was in
there has been wiped from the memory, so, it just blinked
incessantly to tell us that.

Anyway, we narrowed the problem to the fact that the flame wasn't
sensed, and, that meant only one of three things:
1. Bad flame sensor
2. Bad ground for the flame sensor circuit (through the flame)
3. Bad control board sensing of the flame sensor circuit.

I cleaned the flame sensor to no avail.
Replacing the $20 flame sensor solved the problem!

It's amazing that a simple stainless steel rod could fail, but,
it apparently did! Who knows why or how.

The way the flame sensor works is that 90VAC (nominal) is sent
to the flame sensor, which is just a steel rod with a single
electrical connection. When there is a flame, electrons flow
from the steel rod to the chassis ground of the burners through
the flame (rectifying the 90VAC to DC). The flame sensor circuit
on the control board senses the 5ua of DC current, and keeps the
relays on which control the propane gas flow.

The moment the 5ua of current isn't sensed, the control board
shuts down the relays controlling the flame, which is what
was happening. So, there was nothing wrong with the furnace,
other than the flame wasn't being sensed.

With the new flame sensor, everything is working fine.
https://c1.staticflickr.com/9/8565/1...6ed2ba81_b.jpg

What is almost incompressible to me is HOW the flame sensor
failed. It wasn't dirty. It wasn't shorted. It's just a steel
rod! The ceramic wasn't visibly cracked. I just don't get it,
but, it is what it is.

On Wed, 31 Dec 2014 05:22:55 +0000 (UTC), "Danny D."
wrote:

Danny D. wrote, on Fri, 19 Dec 2014 23:56:58 +0000:

It just started getting cold in California, so, the heater power
was turned on, and ... and ... and ... uh ... um ... no heat.
https://c4.staticflickr.com/8/7508/1...4311f464_k.jpg

Update!

The heater certainly hasn't been turned on in a year, and maybe
in two years (as last year was warm). I don't remember, but, anyway,
the problem first looked like a reverse wire but the code was
basically constantly blinking.

As far as I can tell, that just means whatever old code was in
there has been wiped from the memory, so, it just blinked
incessantly to tell us that.

Anyway, we narrowed the problem to the fact that the flame wasn't
sensed, and, that meant only one of three things:
1. Bad flame sensor
2. Bad ground for the flame sensor circuit (through the flame)
3. Bad control board sensing of the flame sensor circuit.

I cleaned the flame sensor to no avail.
Replacing the $20 flame sensor solved the problem!

It's amazing that a simple stainless steel rod could fail, but,
it apparently did! Who knows why or how.

The way the flame sensor works is that 90VAC (nominal) is sent
to the flame sensor, which is just a steel rod with a single
electrical connection. When there is a flame, electrons flow
from the steel rod to the chassis ground of the burners through
the flame (rectifying the 90VAC to DC). The flame sensor circuit
on the control board senses the 5ua of DC current, and keeps the
relays on which control the propane gas flow.

The moment the 5ua of current isn't sensed, the control board
shuts down the relays controlling the flame, which is what
was happening. So, there was nothing wrong with the furnace,
other than the flame wasn't being sensed.

With the new flame sensor, everything is working fine.
https://c1.staticflickr.com/9/8565/1...6ed2ba81_b.jpg

What is almost incompressible to me is HOW the flame sensor
failed. It wasn't dirty. It wasn't shorted. It's just a steel
rod! The ceramic wasn't visibly cracked. I just don't get it,
but, it is what it is.

Congratulations on fixing the problem. However, from an education
point of view, your statement that the flame sensor is just a hunk of
stainless steel is NOT correct. Google "thermocouple" and see how
they work. The current does not go through the flame. It is
generated by two pieces of dissimilar metals creating a voltage which
then causes a tiny current to flow and be sensed. They can and do go
bad.

On 12/31/2014 6:21 AM, Pat wrote:
....

Congratulations on fixing the problem. However, from an education
point of view, your statement that the flame sensor is just a hunk of
stainless steel is NOT correct. Google "thermocouple" and see how
they work. The current does not go through the flame. It is
generated by two pieces of dissimilar metals creating a voltage which
then causes a tiny current to flow and be sensed. They can and do go
bad.

Flame sensors of this type are _not_ thermocouples and indeed the
current is carried by the flame (actually ions produced by the
combustion process). Thermocouples are also used, but they're entirely
different.

It is correct, however, that the flame detector is quite a bit more than
just a chunk of SS...

http://www.gayesco.com/Prod_Flame_Rods.htm

--

On Wed, 31 Dec 2014 09:00:35 -0600, dpb wrote:

On 12/31/2014 6:21 AM, Pat wrote:
...

Congratulations on fixing the problem. However, from an education
point of view, your statement that the flame sensor is just a hunk of
stainless steel is NOT correct. Google "thermocouple" and see how
they work. The current does not go through the flame. It is
generated by two pieces of dissimilar metals creating a voltage which
then causes a tiny current to flow and be sensed. They can and do go
bad.

Flame sensors of this type are _not_ thermocouples and indeed the
current is carried by the flame (actually ions produced by the
combustion process). Thermocouples are also used, but they're entirely
different.

It is correct, however, that the flame detector is quite a bit more than
just a chunk of SS...

http://www.gayesco.com/Prod_Flame_Rods.htm
Thank you for the education. I was not aware of that type.

dpb wrote, on Wed, 31 Dec 2014 09:00:35 -0600:

indeed the
current is carried by the flame (actually ions produced by the
combustion process).

I find it interesting that the electrons flow, in effect,
backward, in the opposite direction of the flame, from the
stainless steel rod, along the flame, back to the burner
metal to ground.

On 12/31/2014 5:45 PM, Danny D. wrote:
dpb wrote, on Wed, 31 Dec 2014 09:00:35 -0600:

indeed the
current is carried by the flame (actually ions produced by the
combustion process).

I find it interesting that the electrons flow, in effect,
backward, in the opposite direction of the flame, from the
stainless steel rod, along the flame, back to the burner
metal to ground.

The primary direction of current flow is determined by the relative
sizes of the two electrodes...iow, it's determined by the geometry of
the detector in relationship to the burner to set up the current flow as
desired.

I didn't find a readable text(*); perhaps the Robertshaw publication
will help some...

http://www.google.com/url?sa=t&rct=j...63_RevB_1.pdf&
ei=t6KkVL29G4qFyQSRw4KYAw&usg=AFQjCNEdbUKV1Mm-cBkT8B4Ui1HGDtt9xg

(*) And, while am a MS Physics guy, I'm not going to try because I find
as soon as I do I end delving far too deeply and confound rather than
explain...

--

dpb wrote, on Wed, 31 Dec 2014 09:00:35 -0600:

the flame detector is quite a bit more than
just a chunk of SS...
http://www.gayesco.com/Prod_Flame_Rods.htm

PHYSICAL CONFIGURATION
1. The flame rod consists of a center electrode and an outer metallic sheath.
2. The electrode is isolated from the outer sheath by an insulating material.
3. The end of the flame rod, in the flame path, has a special high temperature
hermetic seal with a threaded adaptor which is connected to the center
electrode.
4. A high temperature sensing rod is attached to the threaded adaptor.

I'm confused.
Is the "outer sheath" the ceramic?
Or, is the outer sheath the stainless steel rod exterior?

On 12/31/2014 5:48 PM, Danny D. wrote:
dpb wrote, on Wed, 31 Dec 2014 09:00:35 -0600:

the flame detector is quite a bit more than
just a chunk of SS...
http://www.gayesco.com/Prod_Flame_Rods.htm

PHYSICAL CONFIGURATION
1. The flame rod consists of a center electrode and an outer metallic sheath.
2. The electrode is isolated from the outer sheath by an insulating material.
3. The end of the flame rod, in the flame path, has a special high temperature
hermetic seal with a threaded adaptor which is connected to the center
electrode.
4. A high temperature sensing rod is attached to the threaded adaptor.

I'm confused.
Is the "outer sheath" the ceramic?
Or, is the outer sheath the stainless steel rod exterior?

As it says, the center electrode is isolated from the outer metallic
sheath by the ceramic. IOW, it's a center rod in the center of a
ceramic insulator all surrounded by the outer case that you see. It's
not a "rod" at all but a composite assembly that looks solid from the
outside.

--

Pat wrote, on Wed, 31 Dec 2014 07:21:06 -0500:

your statement that the flame sensor is just a hunk of
stainless steel is NOT correct. Google "thermocouple"

We thought the same thing too... at first.

On 12/31/2014 12:22 AM, Danny D. wrote:

With the new flame sensor, everything is working fine.
https://c1.staticflickr.com/9/8565/1...6ed2ba81_b.jpg

What is almost incompressible to me is HOW the flame sensor
failed. It wasn't dirty. It wasn't shorted. It's just a steel
rod! The ceramic wasn't visibly cracked. I just don't get it,
but, it is what it is.


I've forgotten that information. But
still, results is what counts. I've
also replaced a couple sensor rods.

Now, on to the next repair. With 500
posts, 50 Flickr pictures, and 4,000
reply posts from the list.

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

UPDATE:

The heater has been working (although it has been almost 70 degrees
lately) just fine with the new flame sensor.

Apparently, this is what happened:

1. Heater wasn't working for so long that it "forgot" the prior
error code, so it was just blinking incessantly.

2. Eventually, the heater got around to blinking a code for a
bad flame sensor circuit.

3. The observation was the flames would light and then shut off
within seconds, four times, and then lockout would occur until
the power to the furnace was turned off and back on.

4. All measurements to determine whether the flame sensor was
broken had failed, mainly because 5uA is hard to measure and
because the meter I had borrowed must have a blown fuse.

5. However, replacing the flame sensor worked.

How the flame sensor failed is a mystery, as it clearly was not
tarnished (it was sanded with steel wool, emery cloth, and a file,
over subsequent attempts). The ceramic "looked" intact, but may
have developed a fault such as a crack.

The assumption is that the flame sensor failed, although the
only proof of that is that the new flame sensor worked as
soon as it was installed.

Thanks for all your help and advice.
Who knew that the flames form part of an electrical circuit!

If you really want to verify a bad flame sensor, wait till spring,
and put the bad one back in, and see if the problem comes back.

But wait till spring
Mark

On Fri, 9 Jan 2015 18:16:08 -0800 (PST), wrote:

If you really want to verify a bad flame sensor, wait till spring,
and put the bad one back in, and see if the problem comes back.

But wait till spring
Mark

.... or wait until the new one fails and then try the old one

chuckle

makolber wrote, on Fri, 09 Jan 2015 18:16:08 -0800:

But wait till spring

On Sat, 10 Jan 2015 00:11:04 +0000 (UTC), "Danny D."
wrote:

5. However, replacing the flame sensor worked.

How the flame sensor failed is a mystery, as it clearly was not
tarnished (it was sanded with steel wool, emery cloth, and a file,
over subsequent attempts). The ceramic "looked" intact, but may
have developed a fault such as a crack.

The assumption is that the flame sensor failed, although the
only proof of that is that the new flame sensor worked as
soon as it was installed.

Thanks for all your help and advice.

Doesn't the flame sensor have a "special" metallic coating? Sanding
it off will damage the sensor?

Who knew that the flames form part of an electrical circuit!

I think my HVAC furnace has a safety feature. When the flame goes out
the gas shuts down the gas valve. Wonder if it via the sensor?