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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a 90 error code on my Honeywell IAQ thermostat

Customer Question

i have a 90 error code on my Honeywell IAQ thermostat indicates data interface is continuously busy. is it a t-stat modual problem?
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, it could be a thermostat module problem, or bad wire connection at the air handler unit where the thermostat wires connect, or the printed circuit board is bad (same board where the thermostat wires connect).

Tell me a lot about you appliance repair type skill set, I can coach you a bit, or offer an additional service if you want training.

We can go from there.

Expert:  Phil replied 1 year ago.

I need to know about how old the system is as well.