Goodman gmpn060-3 ... Burner stays off

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Old 01-03-08, 09:42 AM
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Goodman gmpn060-3 ... Burner stays off

Hi.

I am new to this forum. I have a 5 y/o Goodman gas furnace, gmpn060-3 with serial #9902601148.

It seems that the fan works (when I put the controller on On and no heat, the fan works fine), but when I put the control on ON / Heat or automatic heat, the fan works in/out and the burner doesn't stay on.

I observed it for few minutes. The burner turned on twice in 10 minutes, but immediately turned off. I had the same problem last year, when it got really cold suddenly, and a pro came and fixed it. I think he replaced a thermostat part and it was working just fine till yesterday.

Any suggestions? besides paying him another $80!!
 
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Old 01-03-08, 10:38 AM
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With this furnace, I'd check to see if the pressure switch is shutting the furnace off intermittently. You'd need to use an AC voltmeter to measure the voltage on both sides of the pressure switch. One side should get 24 VAC as soon as the thermostat calls for heat. The other side should switch on the 24 VAC when the inducer motor comes up to speed, and it should stay on as long as the thermostat calls for heat.

If the voltage shuts off when the burners go off, let me know.
 
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Old 01-03-08, 10:59 AM
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SP, Thanks for your reply.

I am sorry but how do I know which one is the pressure switch?

And if indeed this seemed to be the problem, do I need to change the pressure switch? Something I could do it myself?
 
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Old 01-03-08, 11:10 AM
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The pressure switch usually has a small rubber hose coming from a fitting on it and going to a fitting near the compartment for the burners
 
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Old 01-03-08, 03:49 PM
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Turn up the thernmostat to like 80 and observe burner compartment of furnace and tell us these things:

Presumably your draft motor must be coming on.

Then you must be getting some type of ignition. What kind of ignition do you have?: Glow?; or spark directly to light burner?; or spark to light a pilot flame?

When the ignition takes place and you have burner flame, how long does it last?

The blower motor operation you think might not sound right is probably nothing to do with yor problem. The reason it is acting so sporadical on you is the fact that probably your furnace temp is varying due to your REAL problem, and it simply is shutting off when it is cool and coming back on again after enough heat has built up inside from either one long run of flame or by having the furnace even short cycle for several times in a row, the blower motor can wind up coming on for a bit in such a case, then shut off again.
 
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Old 01-04-08, 09:58 AM
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I turned up the thermostat to 80. First the "Glow" ignition, after about 10 seconds. Then the flames (3 burners) were lit. after 20 seconds the fan kicked in. 20 seconds later the burners were turned off.

So after about one minute from the begining, oonly the fan stayed on and was blowing cold air.

Thnx for your help
 
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Old 01-04-08, 02:13 PM
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The furnace is igniting properly, but the burner is being shut off.



That could be a pressure switch that is opening because the furnace is plugged up or defective in some way, or a dirty flame sensor.


You need to look for a small rod with a wire coming out the bottom that should be in the flames when the burner is on on the side opposite the ignitor. You can take that out and clean it with a wire brush or steel wool and reinstall it and see if that solves the problem.


If not, you need to check to see if the pressure switch is opening. You need an AC voltmeter to test that. One side of the pressure switch will be energized with 24 VAC whenever the thermostat is calling for heat. The other side should switch on and stay on when the inducer motor comes up to speed. If you see the voltage shut off when the burner shuts off intermittently as you describe, let us know.
 
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