Furnace parts- need help troubleshooting a problem with furnace.

Werner007

Good evening,

My question concerns the following equipment,

Model number - G40UH-488-090-07

A Lennox furnace

Problem description: Blower motor was not starting even with the fan at the "on" position. I fiddled around with the wires on the control board and found that the motor starts if a bundle of wires that all go into a plug  (12 pin wire harness?) are help up or rather pushed upwards. This seems to reestablish electrical contact thus starting the motor.

My question is...where can I buy this part (the wire harness). I've attached a picture to this post. It is the white plug that goes into the control board towards the bottom right side (partly obscured by the red wire). It is being pushed upwards by duct tape. The furnace is working but I may eventually need this part.

JUGHNE

If you look at the back side of the board you might see some burn marks where that connector is. If so you need a new board.

A "Bic" ink pen with the guts removed might fit on the white plastic stand offs to depress the tabs.....trim pen as needed.

mattmia2

I always used needle nose pliers to release those while pulling on the board so it would slip over the barb once I compressed them enough.

Probably can clean up and re-solder the bad joint. Scrape the solder mask back a little bit more than it was originally so the solder gets better contact with the trace. Sometimes I have wrapped a few strands of wire around the terminal or lead and filled the whole area with solder in particularly underengineered boards or terminals to keep them from overheating and failing again. Sometimes you have to clean the terminal with a wire brush to get it to tin properly.

STEVEusaPA

I'm not soldering a board, nor would I recommend that to a homeowner. That's a huge liability to me if it doesn't shut down on limit and I soldered it-whether it was my fault or not.
If it needs a new board, it needs a new board. Just make sure it's not the molex plug, or one of it's connections. Otherwise it still won't work but you end up with a spare board.

mattmia2

There are technical details to every repair that you must get right for it to be safe. Repairing a solder joint is pretty low on the scal of those risks. You are much more likely to misconnect or short something removing and replacing the board that creates a safety hazard than you are repairing a terminal connection.

Big Ed_4

I would replace the board and the harness to the motor ..

JUGHNE

If a contractor were to solder the board perfectly and if functioned as designed......but then the gas valve is mechanically stuck open by debris and the house is torched.
All that would be remembered is the guy who "fixed" the control board.
The saying goes "what do you call a contractor in a jacket and tie....the defendant".

Werner007

Thank you all for the helpful advice.