Lennox GWM 100IE main control board (probably) issue

Cold_in_AK · August 2023

Hello all, i am having trouble with my Lennox wall mounted boiler, it will randomly stop heating, and shows "No Comm mainboard" on the user interface module (perpetually) of i reset the house breaker it will start heating again and respond to calls properly.

I've had 2 different companies come out to look at it, oth of them have functionally scratched their heads, with the second company saying "replace the mainboard AND user interface".

My question is 2 fold

1. Does this sound like a main board/ user module issue? It seems that way to me but i am not an expert and if there is a different solution I'd want to run that down first.

2. Are Dunkirk/Utica parts compatible with Lennox? The second company is wanting to charge over double what the cost of the parts is online from Dunkirk (not including technician hours, which i am happy to pay) happy to pay for experience but getting charged 2.3 times the cost of the parts leaves a bad taste in my mouth.

Thanks in advance!

Jamie Hall · August 2023

Check, in order, all connections. Every single plug and every socket. Wires secure? Pins straight? Good tenson on the pins? Not crusty? Just wiggling them is step 1 here! Then, check all the power and ground connections. Solid? Clean? Secure? Do they really have power? Are the grounds really connected? Then check all the wires for any damage -- breaks in insulation, knicks, kinks, whatever.

Then if still no joy you can start worrying about the boards.

Cold_in_AK · August 2023

I can do that sure, i guess i just assumed that having 2 different techs come out to look at it they would have gone through that process (i was at work for both and my wife was working from home so i didn't watch them go through the steps)

Jamie Hall · August 2023

You'd be surprised. First thing a lot of folks do is fire the parts cannon... and it turns out to be a disconnected plug.

Cold_in_AK · September 2023

Checked all plugs and circuts that i could with the multi meter, everything looks good on that end. All plugged in as well, still having this intermittent problem.

Jamie Hall · September 2023

Did you actually disconnect all the plugs and check them and the sockets for any sign of corrosion or tightness? That's the only way to do it -- n a multimeter really doesn't do it, especially for intermittent problems.

Cold_in_AK · October 2023

Yes, i pulled them all off to test them, bo signs of corrosion or looseness. I went ahead and bought a new main board from dunkirk since it is the same manufacturer for lennox at 1/3rd the cost. Going to be installing that over the coming week and will see if it solves my problem or if i need to get a new user interface as well. Need to get it handled soon cause waking up to a cold house in the mornings isn't going to work for me much longer haha

Lennox GWM 100IE main control board (probably) issue

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