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Phil
Phil, Mechanical Engineer
Category: HVAC
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Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Trane XE 80 comes on when heat is ordered, but then flame

Customer Question

Customer: ***** ***** Trane XE 80 comes on when heat is ordered, but then flame shuts off without error code
JA: Thanks. Can you give me any more details about your issue?
Customer: When turned on, the furnace runs blower to clear out fumes, then the coils glow and gas ignites. after 1-10 minutes, the flame shuts off, but the blower stays on blowing cold air the integrated control is not lit or flashing in short, the gas turns off, but there's no error code flashing
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Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
Are you still working my issue? Should I be waiting here for your response?
Expert:  Phil replied 1 year ago.

Hello, I just got notice of your question. There have been problems with the inter webs today.

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

I can mark it up with trouble shooting instructions.

............

The lack of an error code however points to a bad printed circuit card... lets do a heat stress test on it.

Use a hair drier to slowly and gently warm the card to 120F(warm to the touch but not hot and not over140F)... if you get any change in behavior that means the card is bad.

A micro crack has opened in the printed circuit at a solder joint, or inside its CPU in that case .... or a short circuit has developed as the card expanded when you heated it.

Constant expansion and contraction as these electronics heat and during their duty cycles over the years is what wears these cards out.

It is also a good idea to replug all of the connections in the unit,that burnishes any oxidized terminal connections and will sometimes solve the problem, especially at the printed circuit card and in any sensor molex connectors. Do that with the power off to the unit of course.

We can go from there without a time limit.

Customer: replied 1 year ago.
picture of Trane XE 80 wiring diagram from inside furnace faceplate/cover
Expert:  Phil replied 1 year ago.

Thanks for the excellent diagram.

Have you done the heat stress test on the printed circuit card yet?

With no error code the odds are in the 95% range that printed circuit board is bad.

It is possible but not as likely that the flame sensor rod is dirty. That is a long thin metal rod that pokes into the burner flames, it has a white ceramic base with a wire that runs back to the printed circuit card... that can be removed and cleaned off with plumbers sand cloth... its a long shot in this case however since you are not getting an error code.

The flame sensor rod is shown at the bottom left of the wiring diagram.

We can go from there.

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