AC Compressor short cycling, with a new twist

5448 Views 3 Replies 4 Participants Last post by jblackburn, Sep 23, 2017

billy_j844

Discussion Starter · Sep 23, 2017

The air conditioning on my 2013 LT, with 30000 miles, recently turned warm. The compressor clutch stays engaged just for a few seconds, then drops out. Then engages ... then drops out. Repeats indefinetely. Doesn't stay engaged long enough to do any cooling. I used a low-side gauge, and it reads OK (40 psi or so) during the short cycles. The new twist is that the radiator fan goes into high speed almost from the startup of the cold engine. I'm sure these two symptoms are related--does anyone have a clue what could be wrong? I understand that there's a refrigerant pressure sensor that somehow controls the radiator fan speed--can that be the problem. If so, where is that sensor located? Any help would be appreciated. Thanks in advance.

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Taxman

· #2 · Sep 23, 2017

If you're low on charge, the low pressure switch will shut down the compressor to save it from damage. Then the low side pressure increases as the system equalizes, the low pressure switch sees adequate pressure, and the compressor kicks in again, long enough to drop the pressure on the suction side below minimum and trip the low pressure safety switch again...

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ChevyGuy

· #3 · Sep 23, 2017

I was thinking something more along the lines of air in the system. When the compressor starts, the high side pressure goes sky high shutting down the compressor and triggering the fan to go into high speed (aka jet mode). (High pressure is normally equated to high temperature.)

Either way, you probably need to have the system evaluated by someone who knows A/C systems.

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jblackburn

· #4 · Sep 23, 2017

This happened when my expansion valve went bad. Low side was fine, but high side pressure was sky high. It would cool for 30 seconds or so and then shut off and stay off when it was 90+ outside, and the radiator fan was SCREAMING.

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