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I have a Coleman Furnace Model #DGAA708BDTA. Was working yesterday, then it stopped. ONE LIGHT FLASH on the diagnostic. Two years ago I replaced the booster assembly. Should I try to turn the fan again with a screw driver, or would you suspect something else since it has been working for about a month or so. Pressure switch? Unit is at least 13 year old. Prior to replacing the booster assembly I had to kick start it every year for 4 or 5 years. I had hoped the new assembly would last longer. I hear the furnace kick on, then a humming sound but then nothing happens. The Trane Air Conditioner attached? to the furnace still works, which I guess would eliminate a thermostat problem

Thanks,
pdl2

New or old those combustion motors are prone to seizing. It is humming but not spinning. You could pull it apart, free it and then oil it up. May last another season, may not. Best advice I can give you is to run that motor at least once a month to allow it to not sit for an extended period which usually causes them to lock up.

The problem is that the motor pulls cool moist air in and across itself when being used. This leads to it failing quickly. Why in the heck and design engineer would create an assembly like this is beyond me. Years ago both Coleman and Nordyne had the combustion motor itself out of the intake airflow system. Those motors failed but no where near the frequency the new systems do.

It would seize up that quickly after working the previous morning? what does the "one light flash" diagnostic indicate? where should I oil it and with what kind of oil?

Thanks
pdl2

Should I see the igniter light up before the blower assembly should kick in? or will the igniter not kick in until the blower assembly does first?

Thanks
pdl2

Order of events is: thermostat calls for heat, combustion motor turns on, vacuum switch closes and is recognized by control board, board then energizes igniter, after about 30-45 seconds gas valve opens, igniter must prove flame or gas valve closes, if igniter proves flame igniter circuit is shut down by board and in about 60-90 seconds blower will come on.

If there is an interruption in any of these steps unit will initialize a flash code. NO vacuum switch cannot be jumped out. Board recognizes it opening at the end of the heat cycle.

You mention a ONE flash code on your unit. I think that is a failed ignition code. Usually has nothing to do with the combustion motor or the vacuum switch. Look on the furnace. Those flash codes are all listed.

Yes, "one flash" code is ignition code. So what do I need to check? Looking through, I cant see anything lighting up. Should I see the igniter "light up"?

Thanks,
pdl2

Yes you should see the igniter glow bright orange.