A/C system will not go below 25 inches of water at 85 degrees and 4,600 ft elevation

Tiny
CMCGINNIS13
  • MEMBER
  • 2001 FORD EXPEDITION
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 202,000 MILES
After running for an hour, I close the low pressure side and turn off the vacuum. It holds there for over an hour. I assumed it was due to elevation so I tried to start filling the system with R134A. After starting the car and turning on both A/C at full blast, I open the can of 134 and slowly open the low side, the refrigerant will not flow and my low pressure side jumps to 110 psi. My compressor never turns on.
Thursday, July 11th, 2019 AT 8:22 AM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning,

Was there an issue prior to this procedure?

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

Did you check for power to the compressor?

The vacuum is normal for the altitude.

I attached a diagram for you. Check the fuse circled for power on both sides.

Roy
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Thursday, July 11th, 2019 AT 8:30 AM
Tiny
CMCGINNIS13
  • MEMBER
  • 5 POSTS
Thank you for your response. I recently serviced my A/C system and went for a test drive. The engine temperature was almost red lined while running the A/C system. I turn it off and my temperature came back down, after I got home I turned the A/C system back on and realized my compressor was never turning off. I read somewhere that to replace the low pressure switch the system needed to be emptied. So I had that done and replaced the switch, now it does not come on at all. I checked the fuse and the relay and there both okay.
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Thursday, July 11th, 2019 AT 8:50 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
There is no such thing as the low-pressure switch needing to be emptied.

Do you have voltage at the low-pressure switch?

Roy
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Thursday, July 11th, 2019 AT 9:06 AM
Tiny
CMCGINNIS13
  • MEMBER
  • 5 POSTS
Yeah, I found that out the hard way. I will test for power at the switch and also at the compressor. Unfortunately I’m at work right now.
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Thursday, July 11th, 2019 AT 9:18 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Okay let me know.
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Thursday, July 11th, 2019 AT 9:34 AM
Tiny
CMCGINNIS13
  • MEMBER
  • 5 POSTS
I had to jump the low pressure switch to get power at the compressor. Doing so made the compressor turn on but the system will not pull the Freon into the system. The low pressure and high readings jump to 95 psi both.
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Friday, July 12th, 2019 AT 7:52 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Okay, so you have 95 lbs on both sides and the compressor will not engage? Is that correct?

When it engages, what happens to the pressures?

Are your Schraeder valves working?

Roy
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Friday, July 12th, 2019 AT 8:01 AM
Tiny
CMCGINNIS13
  • MEMBER
  • 5 POSTS
Yes that is correct. 95 before adding anything to a vacuumed system. When it engages nothing changes on the gauges. As far as I can tell my schraeder valves are working.
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Friday, July 12th, 2019 AT 8:48 AM
Tiny
ASEMASTER6371
  • MECHANIC
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It sounds like the valves are not allowing Freon into the system.

Roy
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Monday, July 15th, 2019 AT 3:57 AM

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