So my AC stopped working. The compressor doesn’t come on at all. I know it could be a myriad of problems ranging from fuses, to relays, to the compressor clutch but I’d be willing to bet I have a slow leak and reached the point where the 134a is too low and a pressure switch keeps the compressor clutch from engaging when I tell it to.
Lucky for me I’m an engineer at an industrial oxygen concentrator manufacturer so I have access to a myriad of pressure gauges. Anybody know what the high side and low side pressures in an automotive AC system should be? Can I measure them without the compressor running? Any other tips?
My '01 Jetta. I’m guessing it’s just low on 134a, but I want to get a positive diagnosis before I spend any money since it looks like this could potentially get deep quick. But hey, it’s a VW. Expensive repairs are few and far between… :ham:
Don’t buy any refridgerant until you see if there is pressure in the system.
If there is, there is probably not a leak (at least not a huge one). If you are impatient like me, I’d see if there was pressure, fill it up and call it a day.
But if you were smart, you’d check the pressure, wait a couple of days, and check the pressure again to see if it went down.
High side: 175psi
Low side: cycle between 30-45 psi (depending how good the compressor is)
Keep in mind these are just ball park! Look them up in the service manual for your car. If your high side pressure is low (usually around 75-100 psi) the pressure switch will not cycle the compressor so it avoids damaging itself.
Thanks guys. Sometime soon I’ll look and see if I’m in the triple digits on the high and double digits on the low. If things look low then I’ll probably fill it up, then monitor the pressures over a couples days, then week, then month. Hopefully it’s been leaking since it left the factory and took 5 years to hit the low set point.
I’ve never topped up an AC system. I’m guessing I fill the low pressure side, run the system, and check again?
OK, so I got the little refrigerant refill kit with a gauge. I located both ports (high and low.) One is up at the passenger side firewall and is a large fitting. The other is near the radiator and is a small fitting. The fitting on the kit does not fit over the large port. The small port is at 150 PSI. So what gives? Is my low pressure side at 150 psi, meaning something in my system is all sorts of fucked up? Am I retarded and just not able to put the kit on the true low pressure fitting?
While not running the system should equalize its pressures I believe. My guess is a compressor clutch relay. Goodluck let us know if theres any more we can do to help.