Question about Goodman GMS90703BXA Heater

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Shutting off on pressure sw. 2 yr old goodman counter flow 80+

Unit in closet question whether switch is bad or blockage in flue or elsewhere. The inducer blower seems to be fine.
What should pressure be at inducer or switch?

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  • Anonymous Mar 27, 2014

    Open pressure switch no power going to inducer motor



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The problem is your gettign a code and the legend is telling you its the pressure switch? From your description.

Well it is going to be rather difficult for you to check the switch without a .10" gauged water manometer gauge. It would be easier and cheaper for you to purchase another switch but if its only 2 years old the factory warranty is usually 5 years on parts. All you'd owe for is labor and freight if you have to have it sent to you. Take your model and seril no and go to who you purchased iot from and tell them what code your getting.

Some of these pressure switches and the boards that control them look for the switch to acuate both ways on and off knowing that the switch is actually working and not stuck. So you could start out by jumping the correct NC normally closed circut turn on the furnace and remove this jumper and then close the NO normally closed circut with a jumper. This isnt a fix but may help you see if the switch is actually at fault. If you get it to lite off let it cycle back off and note if it works all way through the cycle. If it does Your problem is most likely the switch because you just did all it does only by hand. DO not leave it this way because you can cause a more seveer problem and it is can develope dangerious consequences. This is just 1 way to check the switch. Another way is to check it electrically. If your femilur with open and closed circuts check across the closed and open circut whith it off then with it running and (if it has 3 terminals wires in, if it just has 2 wired in then it is not going to look for one of the operations Ive discribed). And then check and see if the voltages reverse while beginnign to lite off. If it does reverse Im betting you have a different problem and the swich is what the board has been told is giving the trouble.

Hope this is clear. If not get back to me. If it helps please grade me accordingly. THANK you and GOOD LUCK

Posted on Mar 04, 2009


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Furnace won't stay running

Furnace fails to operate.
• Integrated control module
diagnostic LED is
flashing ONE (1) flash.
• Furnace lockout due
to an excessive
number of ignition
“retries” (3 total)1.
• Failure to establish flame.
Cause may be no gas to
burners, front cover
pressure switch stuck open,
bad igniter or igniter
alignment, improper orifices,
or coated/oxidized or
improperly connected flame
• Loss of flame after establishment.
Cause may be
interrupted gas supply, lazy
burner flames (improper gas
pressure or restriction in flue
and/or combustion air
piping), front cover pressure
switch opening, or improper
induced draft blower
• Locate and correct gas
• Check front cover
pressure switch
operation (hose, wiring,
contact operation).
Correct if necessary.
• Replace or realign
• Check flame sense
signal. Sand sensor if
coated and/or oxidized.
• Check flue piping for
blockage, proper
length, elbows, and
• Verify proper induced
draft blower performance.

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