A/C blows hot and compressor has no power to it

Tiny
DOGHOUSE TENET
  • MEMBER
  • 2005 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 183,000 MILES
My A/C blows hot, compressor clutch does not engage and the electric fans don't turn on. The system is charged and I have power to the relays and fuses, the pressure switch and the dash controls. My voltmeter does not read power at the compressor or fan connectors. I have found the ground wires on the chassis and cleaned them but still didn't fix the problem.
Friday, June 26th, 2020 AT 9:00 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

If you have power to the low pressure switch, does the power come out to the compressor? If you jump the low pressure switch, does the compressor engage? Also, if you look at the attached pic, note that the ground for the low pressure switch is spliced. I'm not sure where you checked.

Also, if you look at pic 2, is there power out from the relay (dark green wire)?

Let me know. Also, let me know what the static pressure is in the system.

Take care,
Joe
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Friday, June 26th, 2020 AT 9:30 PM
Tiny
DOGHOUSE TENET
  • MEMBER
  • 2 POSTS
The relay has power, it's a good relay, I tried to the jump the pressure switch and got nothing. I tested the connector at the compressor and it is not reading. I used the chassis as a ground point as well. I have 5 chassis ground and I cleaned them all. There are two grounds on the back of the engine block that are on tight, I couldn't get a tool down there without diving deeper into disassembly. And by that time it dark and my frustration wasn't going to help me. However the ground wires leading to them looked in good shape.
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Friday, June 26th, 2020 AT 10:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
When you tested the connector at the compressor clutch, was the jumper in the low pressure switch? And just to confirm, you do have power at the low pressure switch, correct?

If there is no power at the compressor when you jump the sensor and everything else is good, check the power supply wire to the compressor for continuity.

Joe
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Saturday, June 27th, 2020 AT 8:46 PM

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