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AC not cooling

Tiny
RONNIE BUSHA
  • MEMBER
  • 2010 FORD MUSTANG
  • 4.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I have replaced the relay, drier, and high and low side valves. It has low pressure on the high side, and high pressure on the low side. Sometimes it will work for a twenty minutes or so, but most of the time it will not cool at all. Could this be a compressor issue?
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Saturday, June 30th, 2018 AT 5:43 AM

11 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

What are the exact pressures while running?

Does the compressor engage when you turn on the AC?

Are the pressures equal when the AC is not on?

Roy

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak
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Saturday, June 30th, 2018 AT 5:55 AM
Tiny
RONNIE BUSHA
  • MEMBER
  • 6 POSTS
I do not know the exact pressure, all I have is the gauge on the fill can, but it always pegs it in the red.
The compressor does not engage, I have jumped the low pressure relay and it will engage then, but otherwise no.
Yes, the pressure is always reading high in the low side.
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Sunday, July 1st, 2018 AT 4:08 AM
Tiny
ASEMASTER6371
  • MECHANIC
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If you jumped the low pressure switch and it comes on, replace the switch. It needs 20 lbs on the low side to engage the relay.

Roy
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Sunday, July 1st, 2018 AT 5:00 AM
Tiny
RONNIE BUSHA
  • MEMBER
  • 6 POSTS
How many lbs. On the high side?
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Monday, July 2nd, 2018 AT 3:36 AM
Tiny
ASEMASTER6371
  • MECHANIC
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The high side is a normally closed switch. It will open at 375 lbs to protect the compressor.

Do you have the gauges now?

Roy
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Monday, July 2nd, 2018 AT 4:25 AM
Tiny
RONNIE BUSHA
  • MEMBER
  • 6 POSTS
I will have gauges tomorrow. I have already replaced the low pressure relay also.
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Monday, July 2nd, 2018 AT 10:07 AM
Tiny
ASEMASTER6371
  • MECHANIC
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There is no low pressure relay, just the switch.

Did you replace the switch?
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Monday, July 2nd, 2018 AT 10:15 AM
Tiny
RONNIE BUSHA
  • MEMBER
  • 6 POSTS
There was a relay in the fuse box under the hood that I could jump with a wire and the compressor would start running. That is the one I replaced.
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Monday, July 2nd, 2018 AT 10:28 AM
Tiny
ASEMASTER6371
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That is the clutch relay. Jumping it does not mean it is bad. It means the control side was not grounded by the PCM because it did not see the proper signal.

Roy
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Monday, July 2nd, 2018 AT 10:39 AM
Tiny
RONNIE BUSHA
  • MEMBER
  • 6 POSTS
Okay, I got some gauges. At a idle with the AC turned on high, the compressor will not engage and the pressure is 90 lbs on both the high and low side. When I jump the relay and start the compressor the low side drops to 40 lbs and the high side will climb to 325 lbs at that point the fan on the radiator will turn on when that happens the low side drops to 10 lbs and the high side drops to 125 lbs, the the fan turns off and the pressure starts to climb again.
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Wednesday, July 4th, 2018 AT 5:18 AM
Tiny
ASEMASTER6371
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The low side dropping to 10 lbs is no good. It should be 25-30 lbs and stay rock solid.

You have an issue with that but it will not effect the compressor from kicking on. At 20 lbs the system should kick on by itself.

At the very least, you need an expansion valve and a drier.

You need to test for power to the relay key on engine off. There should be two powers present.

Roy
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Wednesday, July 4th, 2018 AT 5:28 AM

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