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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8169
Experience:  Furnace, A/C and heat pump specialist.
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my GMPN080-4 wont ingite

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my GMPN080-4 won't ingite
Hello. My name is XXXXX XXXXX I'll do my best to help. Troubleshooting often requires meters and test equipment. Let's get started and see what we can do.
Are you getting a flash code on the board? If so how many flashes does the light blink between pausing?
Customer: replied 3 years ago.


Since you have replaced flame sensor, according to the service manual, we should look toward gas valve or gas pressure being the issue. Is this in natural or LP? Do you have a volt meter for troubleshooting and are you positive no one has turned off the gas cock in gas line or the little switch on the valve itself? We will go from here.
Customer: replied 3 years ago.

no volt meter. yes the gas (natural) is on. I can smell the gas and hear it flow when it goes through the cycle. the ignitor won't even get hot


Do you have a spark ignition or a glow bar that lights up? Goodman used both.
Customer: replied 3 years ago.

glow bar, it looks fine. no cracks or white spots

Ok, now we should be getting a different code for limits or pressure switch, but lets go through a few steps.

Does the inducer motor come on and do you hear the click at time igniter should start glowing?

Customer: replied 3 years ago.

yes to both

Did you use a direct replacement on the flame sensor?


Customer: replied 3 years ago.

yes i did

Is there any way you can obtain a volt meter? Lowes or Home Depot sells a decent one for about 30 bucks.The reason I say,is we really need to verify if the board is actually sending 120v to that igniter.It is possible that even though igniter was new in box, it could be defective. But our first step is to see if board is doing its job by sending voltage to igniter.
Customer: replied 3 years ago.

i can run down and get one i'll be back in about 30 min


That will be great. First thing we will want to do is unplug the molex connector from igniter and put probes into the supply voltage side from the board. Turn thermostat to call for heat. Allow inducer to come on, pressure switch to close and then we should get a click and 120v to that plug.We will go from here.
Customer: replied 3 years ago.

ok I'm back but I'm not too sure what I'm doing with the volt meter


Give me the model on the meter and I will instruct you


Customer: replied 3 years ago.

southwire 10030s

OK, turn dial to the 200 with squiggly line(App 1:00 on your meter), put probes in red and black connections.

Unplug the molex connector from igniter and put probes into the supply voltage side from the board. Turn thermostat to call for heat. Allow inducer to come on, pressure switch to close and then we should get a click and 120v to that plug

Customer: replied 3 years ago.

i heard the click but all it read was 00.6

Ok, lets follow those wires all the way back to the board white to neutral and black to the terminal on board. Do same thing and see if we are getting 120 out of the board
Customer: replied 3 years ago.

both the white and black go back to the board


also, when i check do i put both leads on for the white wire or one one white and one on black?

That is correct. Put one lead on the neutral terminal of the board where white plugs to board and the other lead to the terminal on board that black plugs to.. ( I think it is marked IGN) on that board
Customer: replied 3 years ago.

it goes to the HSI port, but when I connect the leads like you say, there is an initial reading of 02.5 then drops to 00.0. when it should be clicking over to ignite the gas it only gets a reading on 00.9 then drops to 00.0

Just to make sure I have you right, lets check between the Line 1 black and Neutral terminals on board to make sure it reads 120v (Where power enters the board)
Customer: replied 3 years ago.

yes the supply to the board is reading 120.0


At this point I am starting to suspect the board being the issue. It appears that board is sending signal to inducer, pressure switch is closing and sending message back to board, but board is failing to send the 120v to the igniter.
My first suspicion if igniter didn't light would be pressure switch either not opening or closing or a limit open. You can double check those, be ultimately the board should be giving us a different code if one of them were the issue.
Also you mentioned earlier that you could smell gas as it cycled through.The board should not send any signal to the gas valve to open until the igniter has reached 360 degrees and told board it was ok to open the valve.
Customer: replied 3 years ago.

yeah i can hear the gas hissing and smell it. the ignitor never even gets warm. I know the AC side of the board still works though. So is that still a board issue?


Also, is a board something i can swap out myself or is this something a professional needs to do? I'm only asking since it looks "Plug-and-Play"


A board can fail on any one component as it has a bunch of resistors and diodes on back. Just one of those can go bad and allow everything else to work. I just hate condemning a board without being on site.This is not a real expensive board like some furnaces use, I believe I would change the board. You can buy it for 76.95 from Comfort Gurus.
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