Bryant plus 90 intermittent startup problems


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Old 11-15-12, 01:10 AM
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Bryant plus 90 intermittent startup problems

Bryant plus 90, Model 398AAZ...

I run into a frustrating intermittent problem where my furnace has quit after any of the following scenarios:
1. When only inducer starts, then dies. System is locked up and I have to wait several minutes before turning the power off then back on again.
2. When inducer starts, then pilot lights up, system dies, then is locked up for several minutes before turning power off/on.
3. When inducer starts, pilot lights, main burners light up for about 5 minutes, system dies, locks up for several minutes before off/on.
4. When inducer starts, pilot lights, main burners light up, runs until the thermostat says to shut off, and then may run through multiple cycles before dying, requiring off/on.
The pilot burner was replaced last year. There is no obstruction in the incoming air vent. It appears the condense drain doesn't have any major water collection problems. Filter was recently changed.
Any ideas?
Thanks,
Paul
 
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Old 11-15-12, 02:29 AM
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Replace the inducer motor circuit board.

Clean the pilot burner orifice.
 
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Old 11-15-12, 05:46 AM
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Would this be the 3 wire pilot assy. ?
 
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Old 11-15-12, 07:49 AM
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No. If you trace back the wiring from the inducer motor, it plugs into the inducer motor circuit board.

When the thermostat calls for heat, the inducer motor circuit board should reliably turn on the inducer motor and keep the inducer motor energized as long as the thermostat is calling for heat. From your description of the operation of your furnace, that's not happening, which implies that that circuit board is defective and needs to be replaced.
 
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Old 11-15-12, 04:48 PM
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I think I know the problem

The service guy came and cleaned out my condenser trap. Basically with a 20 year old furnace the trap became clogged restricting the drainage. If the drainage can't keep up, then the water backs into the pressure switch telling it to shut things down and lock up. We cleaned it out and it seems to be working fine. We'll see in a few days!
 
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Old 11-15-12, 06:15 PM
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If the thermostat is calling for heat the inducer motor should turn on and stay on. Your #1 comment said that it was shutting off.
 
 

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