Hi and thanks in advance for any help you can offer. I have 2-Bryant 373LAV Furnace/AC units mounted horizontally in my attic. The 1st floor unit has been operating intermittently when the t-stat calls for heat. I've already confirmed that the stat, fan and AC are operating.. and it's been a hit and miss proposition with the heater. I have not had a chance to go to the attic and check the LED diagnostics codes, or to jumper the terminals directly at the unit. Yesterday I deenergized the 110V power to the unit for about 5 minutes and it went through it's diagnostic routine when re-energized and actually did go through a full heating cycle, but later when the t-stat called for heat there was no response.
I'm looking for any quick checks to keep me from wasting a lot of time and potentially money on expensive control boards, etc. I suspect it may be the electronic ignitor or flame sensor that is preventing the cycle starting, but I know there's a lot of possibilities. If you've experience/repaired this problem in the past.. I'd really appreciate the shared knowledge! Thanks

If LED is present, that's quick step #1. Observe operation, and if anything unusual occurs, check the LED. Dirty flame sensor, faulty pressure switch function, dirty air filters, clogged flue - these are usually pretty fundamental. Service legend with codes should be present on a panel.

Thanks KC-13.. I'll take a look at all of these things. It's in a good mood right now.. was working last night and this morning.

I checked the LED after a fault and got a 34.. checked and cleaned the flame sensor (oxidation) and problem solved! Thx again!