A/C not cooling

Tiny
RUDYPAK
  • MEMBER
  • 2007 LINCOLN MKX
  • 3.5L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 217,000 MILES
Had system checked and charged because no cooling. Lasted about a week.
I put on some gauges on to check pressures. Vehicle was parked for about 45 minutes and outside temperature was about 75 degrees.
Before gauges equalized about 58 and after turning vehicle on with A/C the low side went below zero and the high side went up around 100.
Could it be the compressor?
Tuesday, August 25th, 2020 AT 4:16 AM

2 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Most likely your expansion valve/orifice tube is stuck open or you have a leak. Take a look at this attachment and you will be looking at the 150 and >10. Otherwise you have a leak. I would suggest pulling it down into a vacuum and see if the system will hold a vacuum. If it holds a vacuum then you don't have a leak and need to replace the valve. If it does not then you have a leak that we need to find.

Let us know this info and we can go from there. Thanks
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Tuesday, August 25th, 2020 AT 7:25 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,452 POSTS
When you say checked, what did the check consist of? The loss of refrigerant sounds like there is a leak and the low pressures you post says the same thing. With any charge in the system on a 75 degree day the static pressure should have been higher than 58. Normally 134A static pressures run a bit above ambient temp. So for a 75 degree day if the system has any charge in it you would see about 78-79 psi. That doesn't mean it is full but it has some in it. 59 psi on both sides says it is empty. Then once the compressor was working a properly charged system would show 35-45 on the low side and 150-170 on the high side.
From the numbers you posted the compressor is working but there is no 134A in the system. I would start by finding the leak, it could be virtually anywhere but because it was recently charged you may have a bit easier time by looking at the various fittings and parts for telltale signs of refrigerant oil leaking. Leakage of that amount in a week suggests a pretty good sized leak so it should be easy to spot. Unless it is the evaporator core in the dash, for that you would need to use a sniffer to see if it's leaking as it isn't visible. As the system does build some pressure you can also try the soapy water method where you spray the parts with some water with dish soap in it and look for bubbles. You may want to add some charge to the system first though as the leakage may have pushed much of the oil out and you don't want to chance compressor damage.
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Tuesday, August 25th, 2020 AT 7:33 AM

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