Gas and Oil Home Heating Furnaces - Goodman gpd100 goofyness...

Hi all...

My furnace started doing some Dorky things. Click, the little fan spins up, burners ignite, then after just a bit it shuts down. Repeats in some unpredictable ways. The led blinks three times, which the chart say something about pressure switch failure to close.

Does the symptom I so poorly describe sound like it matches what that little chart says?

Thanks for your help...
Dick

Make sure the hose from the pressure switch is clear, and the hose in seated fully over the port.

Or

Is the inducer motor sounding odd? (Poor bearings, or blade scraping on something)

No odd noises. All sounds smooth. Just the click of the cycling.

Ok, just check on the hose(s) to and from the pressure switch to make sure all is good.

Take the hose from the exahust fan housing and blow and suck on it very soft to see if you can the pressure switch working.

Will do. Thank you, I will check back tomorrow.:thumbup:

the hose blows clear, and I can hear the switch clicking as I breathe in and out on the switch. Next?

Thanks again...

Do you have a meter to see if the switch is open and close as needed?

How is the roof cap look on the roof? Nothing is blocked or gotten into the chimney?

Hi all...

My furnace started doing some Dorky things. Click, the little fan spins up, burners ignite, then after just a bit it shuts down. Repeats in some unpredictable ways. The led blinks three times, which the chart say something about pressure switch failure to close.

Does the symptom I so poorly describe sound like it matches what that little chart says?

Thanks for your help...
Dick

Maybe not. There should not even be ignition if the pressure switch were "open" upon ignition. I don't put 100% faith in those charts. Most recently I had a gas water heater tell me the pressure switch was open. Yes, it was open alright, (NOT) because the entire smart valve was bad - not even allowing current to even get -TO- the pressure switch. I correctly replaced the smart valve and that fixed it.

Maybe it is just a flame sensor that needs cleaning. But do what Jay suggests and check to make sure the pressure switch and all safeties are "closed" (allowing passage of ~24VAC current) when the inducer motor runs.

I wish I knew where to test. Is there a manual somewhere I can download with diagrams? I am not heating guy. I didnt even sleep in a holiday in express last night...:D

There's a diagram on back of the blower door.

Just put your meter across the two pins on the pressure switch, and if you read 24 volts, the switch is open, 0 it's closed.

Well, I got 25.5 volts from the switch, and was able to confirm open/closed by checking resistance while blowing and sucking.

I also took the flame sensor out and cleaned it. And, I checked to make sure the opening in the draft inducer wasnt blocked.

What's next?

Thanks again for your help...

Follow the wire in series to see if there is another switch/limit in line of the pressure switch.

What is the full model # on the furnace?

Its a goodman gpd100-4. 1993 model.