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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7910
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My AC stopped working and my Honeywell T8775 thermostat (no

Customer Question

My AC stopped working and my Honeywell T8775 thermostat (no batteries) has a blank digital display.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello,

The thermostat wires terminate inside the furnace. If you can locate those and use a multi meter to check for voltage between the red wire and the gas valve body.. and the read is less than 11 volts, then the 24volt power transformer in the furnace has failed, or the 3 amp fuse usually found on the printed circuit board has blown... if you get 24v between red and any of the other wires attached to the thermostat terminal strip in the furnace... then the thermostat is bad, or there is a broken wire between the terminal strip and thermostat.

I will coach you on any of that as needed, meantime tell me a lot about your skill sets and if you have a multi meter or not... that way I can coach you most effectively.

If I miss you tonight, I will be back first thing in the morning.

...........

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