First post, already with a question! :laughing: Hoping that the DIY crew can help either confirm my diagnosis or send me on to look at a few more things.
Equipment: Bryant Plus 90
Model: 350MAV048100
Control Board: HK42FZ011
Age: ~13yrs / 1997?
Situation: We have a 2-story home and quite often keep our fan set to "On" rather than "Auto" to help keep the temp upstairs somewhere in line with the temp downstairs, always tends to be colder up there in the winter, warmer in the summer. I came home from work on Friday and found the house to be a bit stuffy, so I went to the thermostat and flipped the blower to "on." In Michigan this time of year, we haven't yet fired the A/C - usually just circulating the air on a warm spring day is plenty.
After switching on the blower, I realized that it was quiet - blower not running. No blower or inducer blower, from what I could tell, whether demanding cool or heat. In heat, no action at all, simple as that. In cool, the outside compressor kicks on, and I can hear the circulation in the A/C lines but the blower never spins up.
Diagnoses so far: I hopped on the computer and started searching/reading. My initial fear was that the blower itself had failed. I also came across some info suggesting that a wonky thermostat could cause such problems as well. So:
From info I've read here and elsewhere, I need a 325878-751 "conversion" board to service this. I have downloaded a .pdf of the instructions for that kit, looks pretty straightforward.
Seem like a sound diagnosis? I'm not sure exactly what to make of the failed control board test, except possibly to confirm my suspicion that there's something failed or amiss with the board itself. None of the troubleshooting info I can find suggests next-steps when a constant fast flash is returned.
I currently have the blower bypassed to the door switch as it's been pretty warm the past few days here. I have no problem taking on the control board swap, just looking to some experienced eyes to look over what I've done to avoid a mis-diagnosis or unnecessary board swap.
Thanks for any help or guidance! :thumbsup:
Equipment: Bryant Plus 90
Model: 350MAV048100
Control Board: HK42FZ011
Age: ~13yrs / 1997?
Situation: We have a 2-story home and quite often keep our fan set to "On" rather than "Auto" to help keep the temp upstairs somewhere in line with the temp downstairs, always tends to be colder up there in the winter, warmer in the summer. I came home from work on Friday and found the house to be a bit stuffy, so I went to the thermostat and flipped the blower to "on." In Michigan this time of year, we haven't yet fired the A/C - usually just circulating the air on a warm spring day is plenty.
After switching on the blower, I realized that it was quiet - blower not running. No blower or inducer blower, from what I could tell, whether demanding cool or heat. In heat, no action at all, simple as that. In cool, the outside compressor kicks on, and I can hear the circulation in the A/C lines but the blower never spins up.
Diagnoses so far: I hopped on the computer and started searching/reading. My initial fear was that the blower itself had failed. I also came across some info suggesting that a wonky thermostat could cause such problems as well. So:
- Main Blower OK - I connected the "Cool" blower lead to the downstream-side of the door switch and voila - blower. Nice and quiet, no drama or noise - just a quick, smooth spool-up.
- Thermostat OK - Dug out my old original thermostat from many years ago and connected it. Same phenomena, no blower but compressor kicks on outside when demand for cool.
- Control Board Fuse OK - Visually good, Fluke says continuity OK
- Control Board Test NOK - I connected a test lead to the Test terminal on the control board and clipped it to C/24v. The LED simply flashes at a fast rate. No inducer blower kick-in nor the follow-on sequences. No code, just constantly flashing fast, I gave up counting at 25 fast blinks in a row... :laughing:
- Inducer Motor Spins Freely - A quick check shows that the armature of the inducer blower motor and the blower itself spin freely by hand. Very smooth, no apparent issues like a stuck armature or blower blockage.
- No (apparent) shorts, bare wires, double checked all connections - I unplugged and plugged all main board connections to try to rule out a connectivity problem. Looks OK?
From info I've read here and elsewhere, I need a 325878-751 "conversion" board to service this. I have downloaded a .pdf of the instructions for that kit, looks pretty straightforward.
Seem like a sound diagnosis? I'm not sure exactly what to make of the failed control board test, except possibly to confirm my suspicion that there's something failed or amiss with the board itself. None of the troubleshooting info I can find suggests next-steps when a constant fast flash is returned.
I currently have the blower bypassed to the door switch as it's been pretty warm the past few days here. I have no problem taking on the control board swap, just looking to some experienced eyes to look over what I've done to avoid a mis-diagnosis or unnecessary board swap.
Thanks for any help or guidance! :thumbsup: