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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22673
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Th800 thermostate is showing error code 90?

Customer Question

th800 thermostate is showing error code 90?
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.


this is obscure code that means the thermostat circuit board is reporting as "data interface is continuously busy".

This is a form of a communication fault. It will take a Trane tech to decide if it is the thermostat or the furnace circuit board...generally it is thermostat but would need to be confirmed