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I'm trying to get my AC functioning again after a full engine rebuild over the winter. At time the system was evacuated, completely disassembled, new seals installed and reassembled. I started attempting to recharge by pulling a vacuum with a purpose built pump and gage set on both the high and low pressure sides for about 20 minutes. I then closed the valve to the pump and waited about 30 minutes to check for leaks. iThe gages did not budge so i proceeded to pull the vacuum for about 4 hours in an attempt to pull any moisture out. At this point i started the car, turned on the AC and started to fill from the low pressure side. The clutch kick on as expected but the system seems to "fill" with about half a 12 oz can of refrigerant. Air did not get any cooler inside the car. I then reconnected the gages to the high and low pressure side to see what was happening to the pressures when the AC Clutch kicked on. There is a very small difference in pressure from when the AC is on vs off. I'll post pictures of the gages below in both states. Is this a bad compressor, maybe a bad expansion valve?
AC Off AC On
Last edited by MAVetteGuy; Jul 5, 2020 at 04:53 PM.
I hope this is not an off the wall question, but when you put everything back together, did you install an orifice tube in the liquid line off of the condenser? You mentioned expansion valve but this system does not use an expansion valve, it uses an orifice tube.
Typically, a similar pressure on the high and low side indicates a bad compressor. Are you turning the can on it's side every 10-20 seconds while recharging the system - that can help feed the beast at times also. Hopefully it's something with technique in lieu of mechanical.
I hope this is not an off the wall question, but when you put everything back together, did you install an orifice tube in the liquid line off of the condenser? You mentioned expansion valve but this system does not use an expansion valve, it uses an orifice tube.
I put everything back together about 3 months ago. At the time the AC system was the least of my worries so i cant say i did a ton of research into the system. All i know is that the seals that come with a seal kit for the car were replaced and the system was put back together to the state that it was in prior to disassembly.
Typically, a similar pressure on the high and low side indicates a bad compressor. Are you turning the can on it's side every 10-20 seconds while recharging the system - that can help feed the beast at times also. Hopefully it's something with technique in lieu of mechanical.
Honestly, It didn't even take 20 seconds for the gage to show that it was full.
Here is a diagnostic you can try to see if the compressor might be OK without taking it off the car. It will be necessary to empty the R134a in your system but it sounds like you only have a few ounces in there anyway.
Disconnect the suction/discharge manifold from the compressor. Then plug the suction port with your thumb and rotate the clutch by hand a few revolutions. You should feel two things. 1. The compressor should turn fairly smoothly with no roughness or gritty feel. 2. It should pull a suction on your thumb. This does not guarantee your compressor is good but if it rotates roughly or fails to pull any suction, you will know it is bad. Then put the hose assembly back on, evacuate, and charge it again. One other thing, add the refrigerant with the a/c off. It should take most of the can (If you are using 12 ounce cans), then turn on the a/c to pull in the rest of it if it will take it.
Need Help Diagnosing AC
