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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Had an old thermostat that when using the central air, wouldn't

Customer Question

Had an old thermostat that when using the central air, wouldn't shut the a/c on/off unless I turned it all the way up, or off. Put in a new Honeywell thermostat, following directions to the letter, and now my central air won't turn on.
Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
I called Honeywell, and they suggested that I move the blue wire to a new connection point, but that hasn't worked either. There are four wires, blue, green white and red. On the old thermostat, there were red, white, yellow and green. I believe the blue wire was connected to the yellow on the old thermostat. My central air unit is a Heir 5000, that's connected thru my Heir furnace.
Expert:  gotoman for ac replied 1 year ago.
You may be correct. Older units when yellow was not available used blue to Y on thermostat. Make sure if you have two R connections on thermostat to make sure there is a jumper between them. Russ