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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8063
Experience:  Furnace, A/C and heat pump specialist.
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My Goodman GMH95/GCH9 has been working fine until today.

Customer Question

My Goodman GMH95/GCH9 has been working fine until today. When I turn it on, the vent motor (or some kind of motor) spools up for about a minute and then the flame sensor (the thing infront of the heat exchanger) lights up/glows. But nothing happens, it never ignites. After a couple of minutes it will shut down and try again. But won't ever fully kick on.
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

The normal sequence of operation:

Inducer vent motor comes on

Pressure switch closes

Igniter lights

Burners ignite

Main circulating blower comes on

If furnaces fails before ignition we should get an error code by blinking lights on the control board. Turn power off and back on, then call for heat.tell me how far in that sequence it goes and what error code is on first failure We will go from here.

Expert:  airheatman replied 1 year ago.

Control board will be in blower compartment

Customer: replied 1 year ago.
the vent motor comes on
i can't tell if the pressure switch closes, I hear a clicking noise so maybe it is
the click allows the igniter to light
and then nothing. the vent motor keeps running for a few more second, turns off, and then the cycle repeats.
I'm getting a steady/continuous single blink on the red LED.
Expert:  airheatman replied 1 year ago.

Ok pressure switch is closing if igniter starts to glow. So lets start there.Do you have a volt meter for troubleshooting?

Customer: replied 1 year ago.
Unfortunately not.
Expert:  airheatman replied 1 year ago.

Let me ask you tis. After the igniter glows do you hear the gas valve click or any slight brief odor of gas?

Customer: replied 1 year ago.
When the igniter glows I do hear a click that sounds like it's coming from the gas valve but I do not smell any gas being released. I checked my tank and the gauge showed 50% full.
Expert:  airheatman replied 1 year ago.

We really need to know if the board is sending 24 volts to the valve to know how to proceed in troubleshooting so we are not guessing.You can get an inexpensive one at Walmart for about 15 bucks if you would like.

Customer: replied 1 year ago.
I can get one tomorrow and then report back to you when I have it so we can test for the 24V.
Expert:  airheatman replied 1 year ago.

That will be great.That will tell us if the gas valve or pressure may be the issue or if board is never calling for the valve to open.

Expert:  airheatman replied 1 year ago.

Just make sure to get a meter with leads and that reads actual voltage, not just on of those little 120 volt test lights that shows if a circuit is hot or not.Here is a sample.

http://www.walmart.com/ip/37156640?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227024862248&wl0=&wl1=g&wl2=c&wl3=42965978432&wl4=&wl5=pla&wl6=81457925912&veh=sem

Customer: replied 1 year ago.
Okay sounds good! I will just bring one home from work tomorrow. I'm an engineer for an automotive company but I've never messed with furnaces before so it's all new territory for me lol I will message you tomorrow when I've got everything ready to go!
Expert:  airheatman replied 1 year ago.

Sounds great. If you happen to have access to a manometer or a gas pressure tester, bring that too. If we are getting 24v to valve we need to check inlet pressure to valve next.Talk tomorrow.

Customer: replied 1 year ago.
I am home now with a voltage meter! I wasn't able to acquire any of the other instruments.
Expert:  airheatman replied 1 year ago.

OK set the meter to AC volts. Lest put one lead on each of the gas valve terminals and call for heat.When igniter glows watch to see if we are getting 24v ac to valve.

Customer: replied 1 year ago.
Just to clarify the gas valve terminals...i see a plug in to the valve that has 3 wires (red, brown, brown). Do I put one a red and one on the far brown?
Expert:  airheatman replied 1 year ago.

What are the terminals labeled?

Customer: replied 1 year ago.
from left to right: HI C M
Customer: replied 1 year ago.
I also noticed too that the red LED is solid (normal operation) before it tries to ignite. When it fails to ignite it flashes once which according to the chart means "system lockout, retries exceeded".
Expert:  airheatman replied 1 year ago.

Ok on the mode switch on board are you set to 1STG or 2STG on dip switch?

Customer: replied 1 year ago.
It is set to 1STG currently
Expert:  airheatman replied 1 year ago.

Ok we should get 24v between both C and M and between C and HI

Customer: replied 1 year ago.
When the board clicks to send the 24 volts my volt meter light lights up red and then when the board gets off to stop the 24V the red light goes out. So my assumption is that no I am not getting the 24V to the valve.
Expert:  airheatman replied 1 year ago.

What is model on meter? Does it not read actual voltage?

Customer: replied 1 year ago.
It's a Fluke T5-600. I switched it from AC to automatic selection and tried again. It did pick up 27V when the board clicked.
Expert:  airheatman replied 1 year ago.

OK if we are getting 27v the issue is either going to be gas pressure issue or bad valve.Do you have any other gas appliances that are working properly?

Customer: replied 1 year ago.
I do not. Water heater and stove are electric
Expert:  airheatman replied 1 year ago.

OK our next step is to check the gas pressure into the valve.Without having a manometer or gas pressure tester we are guessing. You can either take a chance that valve is the problem or get gas pressure tested.

Customer: replied 1 year ago.
We have a home warranty so I just filed a claim with them. They should be calling me soon to hopefully set a time to come out.
Expert:  airheatman replied 1 year ago.

Excellent. Thanks for allowing me to help to this point.