A/C compressor will not turn off?

Tiny
CHARLES MESLER
  • MEMBER
  • 2001 FORD F-250
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 250,000 MILES
The compressor started clicking on and off abnormally. The air is still always blowing cool, but not always as cold as normal. Especially the longer I drive. Now the compressor stays on all the time when turned on. Clutch does disengage if I turn the A/C off. Hooked up gauges and low side was extremely high. I took it to a friend's shop and evacuated the system, ran a vacuum and it held vacuum. Started filling with Freon and at about 30 PSI L 150 H compressor engaged as normal. Same problem though, compressor doesn’t disengage at idle. After 40 L and 190 H psi won’t take anymore freon at 85 degrees. Enough to engage the compressor but still a little low. If I rev the motor to around 2,000 RPMs the clutch will cycle abnormally again sometimes. Leaving the gauges on, turned off the truck and both sides equalized around 95 PSI and held. Always a lot of condensation dripping down since this has started, I assume from the compressor staying on all the time.

Those are the details. I’m thinking since it holds vacuum a leak is not my issue, and since both sides equalized at a normal rate and held, blockage isn’t either. My thoughts are it’s a pressure sensor, and that the increased pressure originally was on the low side it may be that sensor. Which kind of makes sense but also not. Idk. I have a basic understanding of a/c but am by no means an expert. And any research is ambiguous at the least. I kind of want to just replace both sides sensors and see what that does. I can easily find the low side sensor, but I can’t seem to find online where the high side sensor is. And when I look up the parts, it only gives one model. Are they both the same? Any guidance would be much appreciated.
Friday, August 4th, 2023 AT 1:41 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,949 POSTS
At 40 L and 190 H psi the system is low on refringent. At about 90 degrees outside air temp the high side should be at about 250 psi. The charge cans or keg have about 65 PSI so the system should take more. Please go over this guide:

https://youtu.be/4EqdrBVb0sY

Here is the high side pressure sensor location in case you want to change it out. Check out the images (below). Please let us know how it goes.
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Friday, August 4th, 2023 AT 12:49 PM

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