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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 Honeywell PRO TH4000 thermostat in our upstairs

Customer Question

Hello, I have a Honeywell PRO TH4000 thermostat in our upstairs zone. It activates the heat but not the AC. The AC in the downstairs zone works. I made sure the set temp is cooler than the inside temp. I flipped the breaker for the compressor and the AC unit in the attic and still nothing.
Can you please help?
Submitted: 2 years ago.
Category: HVAC
Expert:  gotoman for ac replied 2 years ago.
Check zone panel and make sure light for that zone is coming on.. Observer damper and see if arm is moving opening damper. Shut down system all dampers should fail in open position. Turn on fan to see if you get air flow. Russ
Customer: replied 2 years ago.
What is a zone panel and a damper? Where do I find them?
Customer: replied 2 years ago.
Never mind. We called a guy. I thought I was going to get an answer on Sunday night.
Customer: replied 2 years ago.
The answer was that there was a disconnected wire inside the thermostat.

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