Heat Pump Defrost Cycle Failure

7 years ago

In all my troubleshooting and searching, I have learned the AC will not run. Fan goes on but outside unit does not. When selecting heat pump, unit goes into defrost cycle but fails to come out of it and will not defrost- hapens when its cold or even now at 60 degrees. I believe I may have a faulty York S1-025-32701-016 10K Ohm Temperature Sensor. Can someone tell me how to test my old one? I have it in a glass of ice water with no resistance and no change when it warms up.

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fsq4cw

7 years ago

I might be wrong (I don't think so!), so feel free to correct me.

My recollection is that during defrost cycle to melt the ice on the HP coil, that the indoor fan coil runs in AC mode with the electric backup elements ‘ON’ to ameliorate the cold air blowing through the ducts while in Defrost Mode. The outdoor HP compressor runs because it is in AC mode. The HP condenser coil outdoor fan does not run, to complete the ice melting function as quickly and efficiently as possible.

IMPO

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Comments (6)

fsq4cw
7 years ago
I would suggest putting the sensor in the freezer for some time and then measuring its resistance immediately when placed at room temperature. Continue to measure resistance over time, say 1-hour at room temperature. There should be a change in resistance as the sensor warms up if it’s purely resistive. If there is no change, if it is and remains ‘Open’ (high resistance) or if it is and remains shorted (low resistance) then there is likely a problem with sensor.

Which fan are you talking about, the fan coil blower or HP fan? It’s normal that the HP fan does not run during defrost but the compressor does.

IMPO

SR
weedmeister
7 years ago
The blower fan will run during defrost, as well as the compressor fan.
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dadoes
7 years ago
The condensor (compressor) fan on my Carrier heat pump, and the Lennox I had at a previous house, do not run during defrost.
kevinande
7 years ago
fsq4cw, that is how mine operates. No condenser fan during defrost.
wdccruise
7 years ago
The part is on ebay for $25. Just an fyi.