A/C clutch will not run unless it is jumped at relay or low-pressure switch?

Tiny
DAN HOOKS
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 7.4L
  • V8
  • AUTOMATIC
  • 178,000 MILES
The A/C was charged, and I turned on clutch on via me jumping the relay on the fuse box to make clutch come on, low temperature sensor was replaced and relay changed, but clutch still won't run unless its jumped at relay or low-pressure switch.
Friday, July 19th, 2024 AT 9:47 AM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
The low-pressure switch could be telling you there is a leak in the system. Can I ask if you jump the relay, and the compressor runs does it make cold air? When you had the system charged was it flat or did you do it yourself? Let's see if there is any refrigerant left in the system by following this guide:

https://youtu.be/-mikngtS63w?si=JX-3esKd7xCz5jwn

This guide can help as well:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Please go over these guides and get back to us.

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Friday, July 19th, 2024 AT 12:28 PM
Tiny
DAN HOOKS
  • MEMBER
  • 11 POSTS
It has Freon in system 135 H 55 L.@ 85° Its Cold 41°` when I jump ether one, low pressure switch or relay. System blew a line from a over charge 3 years ago. I just now replaced the line and pulled a vacuum, it held, I charged System. Clutch refuses to run unless jumped. It gets cold if I jump relay or low pressure switch.
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Friday, July 19th, 2024 AT 9:19 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
If the system has a charge and it runs if you jump the pressure switch then I would replace the pressure switch.
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Saturday, July 20th, 2024 AT 10:10 AM
Tiny
DAN HOOKS
  • MEMBER
  • 11 POSTS
I did, still must jump it!
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Friday, August 2nd, 2024 AT 6:31 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Hmm, makes no sense there, the pressure switch should connect the circuit, maybe you got a defective pressure switch?
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Friday, August 2nd, 2024 AT 9:33 AM
Tiny
DAN HOOKS
  • MEMBER
  • 11 POSTS
I changed both in parking lot still didn't work right. Cabin switch maybe?
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Friday, August 2nd, 2024 AT 4:39 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Not if you jump the low sensor and the A/C works. The problem is the low-pressure sensor, with the system off what is the residual pressure?
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Saturday, August 3rd, 2024 AT 10:34 AM

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