Troubleshoot GMP Goodman part 1

This is a list of the common problems with the Janitrol GMP 050, 075, 100, and 125 -3 gas furnace.
this vid will be combined with some others on this furnace to cover more specific problems.
This video is part of the heating and cooling series of training videos made to accompany my websites: and to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

11 Replies to “Troubleshoot GMP Goodman part 1”

  1. I have a GMP-050-3 Rev B, the inducer starts, lights the igniter, you hear the gas valve click, it lights the burners, burns for 3-5 seconds, then the flames on the burners go out, the main blower starts about the time the flames go off, I have replaced the flame sensors, checked the limit switches for continuity all were closed and there are no trouble code lights on the board. It will try to relight a couple more times but never fully cycles, any ideas?

  2. Is the burner box suppose to have 4 sealing washers between the box and the heat chamber, where it mounts up?

  3. My 20 year old, horizontal, mounted in attic GMP 050-3 Rev B furnace's circulating fan just stopped running today. Furnace lights off and fires up fine- but the circ fan will not come on. I'm going up there to check the fan start capacitor. If that's good- and the fan motor checks out, I guess its the Control Board…….. Thanks for the video!

  4. I have Goodman 99% furnance Exhaust vent Outside but there's water underneath blower inducer and fan blower side inside then it leaks on basement floor. Wondering if its Condensation pump or Blower inducer?

  5. My gmp125-4 connection to the central ait was iced up outside and i looked at the heat exchanger for tha air and its not iced up but there is water that dripped into the bottom of the furnace below the blower. I cant get the blower to come on and it looks like the status light isnt lit at all on the board. The 3amp fuse is good. I cant even get it to come on in the heat setting. Any ideas? Im hoping water didnt blow the blower motor, but the board should still have a status light. Not sure what points i should look at for power and ground, and the circuit breaker wasnt tripped at the fuse panel. Is there a reset button for power to the board somewhere? Thanks

  6. Hi Gfm, I have the same model and it gets to the set temperature, shuts off and never comes back by itself, i have to flip the power switch off and then on to get it on again, Please help,it drives me nuts, since i have done everything I know and it still not work properly.

  7. First, Merry Christmas! Our Janitrol furnace works great, but every once in awhile it will not come on. All I do is turn the furnace off at the wall, then switch off and on the main power on the side of the furnace, switch the thermostat back on, and we have heat. Are we looking at a bigger issue down the road? I know this isn't normal. Thanks in advance for your help.

  8. I changed the flame sensor and my furnace turns on for a min or two then turns off again what should I check next?

  9. GFM,

    I have the GMP075-03. The fan is only blowing cold air. We have a brand new filter installed. The ignitor glows and starts the flame, but it only lasts a couple of seconds and then shuts off. Would you say this is the Gas valve?


  10. If anyone is still paying attention to this video, I have an issue. I have a GMP 075-3 that the exhaust fan comes on, the ignitor lights, but the gas valve does not click and flow gas. So, the ignitor times out and the cycle starts again. After two or three cycles it finally works. This is an intermittent problem and sometimes it works just fine. Anyone have any ideas?

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