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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8373
Experience:  Furnace, A/C and heat pump specialist.
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My trane comfortlink II has error code 91 and is not working

Customer Question

hellomy trane comfortlink II has error code 91 and is not working
Submitted: 2 years ago.
Category: HVAC
Customer: replied 2 years ago.
I know this is a communication error with my trance xc95m furnace. is it easy to fix? can I bypass the thermostat and have furnace work directly? If I need a new thermostat can I just buy one online and take old off and put new on or do I need professional install. would I just buy another trane xl900 (which is the model I have). are there universal ones easier to get?
Expert:  airheatman replied 2 years ago.
Hello. My name is ***** ***** I'll do my best to help. Let's get started and see what we can do.The error code indicates that the "Common" low voltage wire from furnace is not receiving power at thermostat. This will require some troubleshooting in the furnace to find out why.
The issue is most likely not in the thermostat but in furnace.AS far as replacing thermostat, you can not just use a standard thermostat.This is a "Communicating " thermostat.
These communicating systems are very complicated and usually require an experienced technician to work on them. My recommendation on this is to call in a Trane certified technician.
If this is an emergency and you need heat until you can get in a tech.let me know and I will guide you in a temporary solution.