Heating, Air Conditioning, Fridge, HVAC/Trane XE70 thermal switch

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Question
I have a Trane XE70 furnace in my house.  It's ~25 years old which the model # probably tells you.  My problem is the furnace will only stay on for a short time (~5 minutes) even though the setpoint temperature is far from being reached.  There's a thermal switch at the top of the unit,  kinda all by itself that is opening too soon, shutting off the unit.  The box that it's monitoring is barely warm to the touch so I think it's opening pre-maturely.  There are no markings on the switch.  I've jumpered out the switch and it stays on until the s/p is reached so the switch is the problem.  My problem is I can't find a schematic to show me the p/n for the replacement.  Any ideas??

Answer
Jumping out the thermo switch is a very bad idea.  I would NOT under any circumstance run a furnace without it.  The furnace has to be checked to make sure the switch is not faulty or went faulty because it overheated.  I am not sure if the part is a OEM without looking at it.  If the switch was open and the unit had not run, then I would say it is bad.   I would replace before ever running the unit for more then long enough to check the unit's operation.

Craig
achelpguy@gmail.com  

Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert

Expertise

I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.

Experience

I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

Education/Credentials
5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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