hvac
 

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Question by  kmt33 (43)

What could cause humming in an air conditioning unit when it is not running?

 
+6

Answer by  cooldave (31)

If you have a heat pump, it is the reversing valve and it is normal. May need to tighten or replace solenoid coil if excessive. There may also be a control transformer in your unit, which also has a hum.

 
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