Sometimes heats instead of cools - http://www.hvacmechanic.com/ Forums
Original message
| stevetx
 |  "Sometimes heats instead of cools"
, posted Sun 20 Jul 23:04  
We came home today after being gone about 6 hours and found our house to be over 99 degrees F inside. It is 101 today in Texas and instead of cooling, our heat had come on. This has happened several times now and it't time to get it fixed. We have a Carrier heat pump model FA4ANF048 inside unit and model 38BYC048310 outside unit with a Robertshaw 9620 thermostat. It seems logical that the thermostat is malfunctioning but I thought I should try and trouble-shoot it before going out and purchasing a new one. Could someone give me some advice on how to proceed to check it out, or should I punt and call someone to service it? Thanks, Steve
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Replies:
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| Houston204
| "Re(1):Sometimes heats instead of cools" , posted Mon 21 Jul 06:49
The O terminal controls the reversing valve in your heatpump. This terminal is the problem since you will heat instead of cool without 24VAC to O, in cool mode.
Measure for 24 volts outside between O and C when this occurs. Verify that the reversing valve selonoid is bolted to the reversing valve and not on the floor next to it.
While a Honewell FocusPro or VisionPro stat would be an improvement, my money is on a loose connection or the defrost control.
"Tip of the Day" Remember to remove power first.
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