Thermostat wiring mix-up

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JES2727

Senior Member
Location
NJ
My customer says her husband replaced their thermostat and now the outside A/C unit comes on with the heat. I know it's a simple solution but this isn't the type of wiring I normally do, although I can surely figure it out in a couple of minutes. Can someone save me some time here and tell me what's gone wrong?
 

Minuteman

Senior Member
I 90% agree with Charlie. Another slim possibility is the striped copper from the Y (cooling) terminal is touching the W (heat) terminal and brings on both.
 
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