Original message
| infoquest
 |  "goodman furnace doesn't start up"
, posted Mon 31 Mar 08:27  
I have a goodman gmp075-3 rev A furnace which is approximately 10 years old. The furnace will not start when the thermostat calls for heat. Inspection of the on board diagnostic panel indicated 3 flashes of the indicator LED. According to the diagnostic chart on the door, this means the pressure switch is not closed. Would you explain to me the procedure for checking this device? I have not had good experiences with our local HVAC tech.
Thank you
DAS
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Replies:
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| theduke03
| "Re(1):goodman furnace doesn't start up" , posted Mon 31 Mar 17:39
Shut off your furnace. Check both ends of both vent pipes for a blockage. Remove and flush furnace condensate trap with water. Check all tubes between pressure switch and wherever else they go for blockage/trapped water. Check barbed fittings on tubes for blockage. Then put it back together and restore power. If furnace doesn't run like a champ, then the problem is either a hole in the heat exchanger(terminal) or a bad pressure switch.(unlikely, 90% of the time it's not the pressure switch.)
In CT I would say most often caused by a leaf stuck at the air intake pipe connection to burner. Or outside end of intake pipe clogged w/ snow or ice, or leaves.
You can't put a price on comfort! Be Safe.
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| | infoquest
| "Re(2):goodman furnace doesn't start up" , posted Tue 1 Apr 17:57
Thank you for your response. I am wondering if there are multiple versions of this furnace. Many of the items you suggest looking at are not availble on this furnace. There is no air intake pipe nor can I find the condensate trap. When the furnace is turned on, the vent blower tries to turn on but just pulses and then stops. I don't know how to check the pressure switch to determine if it is any good or not. Is there a method I can use? Also, the vent is connected to the water heater and they both vent thru the roof.
DAS
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| | theduke03
| "Re(3):goodman furnace doesn't start up" , posted Tue 1 Apr 19:57
Oh, I was thinking of another furnace. If you can confirm that the vent motor is being powered with 115v and not running then vent motor assembly must be replaced. It is most likely shot and without it running, the pressure switch will not close.
You can't put a price on comfort! Be Safe.
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| | infoquest
| "Re(4):goodman furnace doesn't start up" , posted Wed 2 Apr 06:16
The power vent is not getting 115v. If there is voltage, it is there only for so brief a time my meter cannot pick it up.
DAS
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| | theduke03
| "Re(5):goodman furnace doesn't start up" , posted Wed 2 Apr 20:21
Bad circuitboard.
You can't put a price on comfort! Be Safe.
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| | Technician
| "Re(2):goodman furnace doesn't start up" , posted Mon 31 Mar 18:55
If that furnace is 10 yrs.old you should check the heat exchanger. Pay close attention to the crimp rings (especially the lower, front ones) they are notorious for popping off and cracking in these areas.
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