Heating, Air Conditioning, Fridge, HVAC/Heat pump won't defrost


Hi when I jump the sensor pins and speed up defrost unit will defrost. But when I remove sensor wires from board and jump across there it won't. Any ideas?

Hi Steve,

Good question, here's how it works. Coil temperture drops to 28*, sensor closes. Then the timer in the defrost module starts. Depending on which time is selected, 30min, 60min or 90min, then unit goes into defrost.

So to test it at the sensor pins, the jumper would have to stay on for at least 30min. If you want to troulbeshoot this further, let me know what the model number is on the heat pump.  

Heating, Air Conditioning, Fridge, HVAC

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Jim S.


I can answer questions on gas or electric furnaces, ac units and heat pumps. I don't work on boilers,chillers,or home appliances.


I have been in the HVAC trade for over 35 years. For the past 15 years I have owned my own business. I am semi-retired so I can answer questions in a timely manner.

I attended trade school for 5 years on weekends and evenings. This was very hard to do, but well worth it!

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