A/C compressor stopped turning on?

1996 CHEVROLET SUBURBAN
180,000 MILES • 4.8L • V8 • 2WD • AUTOMATIC
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CHARLIE LISTER
AC compressor stopped turning on blower working r134a pressure correct.
Jul 23, 2025 at 2:38 PM
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STRAILER
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  • ASE Certified Mechanic
Hello Charlie,

Can you confirm the compressor is not turning on or the blower motor is not working?

Thanks, Ken
Jul 23, 2025 at 5:11 PM
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CHARLIE LISTER
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Blower is working at all speeds. A/C clutch does not engage.
Jul 24, 2025 at 4:17 AM
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CHARLIE LISTER
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Blower works. A/C clutch does not engage.
Jul 24, 2025 at 4:19 AM
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STRAILER
  • ASE Certified Mechanic
  • 54,497 POSTS
  • ASE Certified Mechanic
Okay, most of the time the system will be low on refrigerant, this will make the clutch not engage so let's check that first. Please go over this video:

https://www.youtube.com/watch?v=uZrQCGwXfek

Let me know how it goes.

Jul 24, 2025 at 9:03 AM
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STEVE W.
  • ASE Certified Mechanic
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  • ASE Certified Mechanic
If you connect a set of A/C gauges and see pressure, that is normal, however it does not mean there is the correct charge in it. That is because it will expand and hold the pressure that equalizes the boil off temperature of R134a. That is normally in the area of ambient temperature. So, if it's 90 degrees you would see around 90 psi in the system regardless of the amount in the system. Then if the compressor is working you would see one side drop to 40-50 and the high side will climb. Those numbers are what counts. If you want to test the compressor you can jump power to the clutch and turn it on with the engine running.
To do that look at the compressor and apply 12 volts to the Dark green wire from the battery. That should engage the clutch. Now watch the gauges and see what the pressures do. If the low side goes down and the high goes up the compressor is at least working. Then the issue is somewhere else, like a pressure switch or wiring issue. Then return and we can look into the issue from there.
Jul 24, 2025 at 2:21 PM
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