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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My furnace will run while after I reset it then I get four

Customer Question

My furnace will run for a while after I reset it then I get four red lights on the status LED. It says it's an American standard model fg8d15020uh11a
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


Please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.

You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here.,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If you have an error code showing, tell me what the code read out is on the wiring diagram or a sticker next to the diagram please.

If there is no paper clip-icon, look for the '+attachfiles'link at left of your send button.

I can mark it up with trouble shooting instructions.

We can go from there.

Customer: replied 1 year ago.
There is no wiring diagram just a sticker with model, serial number, etc. the backside of the door is covered with a fiberglass insulation sheet. I'm attaching a wide shot, a shot of the control board, and a shot of a the burners.
Expert:  Phil replied 1 year ago.

Hello again,

If that limit switch you have been resetting is within 2 inches of the burner it is a flame roil out sensor, that is a dangerous condition if flame is actually rolling out of the fire box and impinging on that sensor.

Those do not often fail, so that I suspect a problem with venting or a hole in the heat exchanger that is blowing the flame out of fire box when the blower comes on.

That is the first possibility we need to check.

Start the furnace and hold whatever buttons in that you have to in order to keep it running, notice the flame pattern closely... then look for any change when the main blower starts... if you see any change or the flame blows out of the fire box, then there is a hole in the heat exchanger. That is cause to replace any furnace over 7 or 10 years old.

Let me know what you can discover, we can go from there.

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