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.