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BHAYDEN69 11-11-2008 06:44 AM

Goodman Furnace won't light Need Help! Thanks
I have a goodman GMP100-3 SN#9402030988...The furnace turns on and the ignitor glows then goes out, it performs this action 3 times then the lite blinks 1 time. I know I'm not getting gas through the gas valve. I am trying to confirm a faulty gas valve. The test I have done is when the furnace goes through its cycles I am checking for voltage of any kind to the valve itself but I never get any voltage. I was told the valve is probably bad but, but my thought was if I get voltage to the valve and it does not open, then its faulty but i'm not sure if this test is correct. Thanks, Brian

kennzz05 11-11-2008 10:27 PM

you are correct you might also hear it click when voltage is supplied you could try jumping it, apply 24v directly while ignitor is glowing and see if it fires if so you know it aint the valve and prolly the board

SD515 11-12-2008 06:21 AM

You’re right bhayden, the valve won’t open until it gets 24V. The schematic label shows how many roll-out and high limit switches it has. Check continuity of those. If any are open, 24V won’t get to the valve. The next question is why a switch is open.

If the valve is a basic 2 wire (probably is), like kennzz said, you can check to see if the valve is working by connecting it directly to the 24V side of the transformer. Be careful…if it is working, gas will come out immediately.

FYI…..I just replaced a valve….did my tests, etc. All the limit switches were fine….the incoming pressure from the meter was too high and caused the valve to ‘wear out’ prematurely. This furnace is only one year old. I see from your serial number yours is a ‘94, so I doubt if you have the same culprit.

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