I know a fair amount about car AC systems but all my knowledge is VW or Chevy. The AC in my new to me R56 isn’t working and I don’t understand the pressures.

Ambient outside temp is about 60 degrees

Ambient pressure with system off is about 70 psi low side and 90 psi high side. (Not sure why it’s different)

System on and clutch cycles, mostly off. Fan comes on when clutch cycles on. Both off same time.

With system on the pressures cycle from 135 psi high side and 30 psi low side. It cycles to 95 psi high side with 35 psi low side.

Is this system over filled? I know modern AC is emptied and proper amount put in but I don’t have that capability.

The temp inside actually increased. No cooling inside.

 

Update: took it over to my son the mechanic and he said it acted like it was low on freon. Got it to run continuously and high side was 75-80.
Put in about 1/4 can of freon and now it’s working and staying between 90-105.

 

Sounds like you have a leak somewhere. The most common cause is a bad O ring at one of the connections, look for a (usually) slight oil sheen at one of the connections. That’s refrigerant oil following the refrigerant out of the system.

Another common cause is the valve where the gauges attach. Everything should look clean and dry.

The hoses should be covered in a light coat of dry dust.

(I know you’re probably aware of this with your experience, this is for others reading the thread)

 

Those pressures seem really low to me. My system cycles high side around 250, though mine could be excessively high. lol

 

I’m guessing you have R134a as a refrigerant, so looking at a Pressure/Temperature chart that equates to a temperature of 140 Deg. F at 250 psi. That’s about what I’d expect to see for the high side.

 

Those are crazy high numbers. Never seen one that high yet.
Should they be the same on a Gen 1? I will check my daughters.

 

My Bentley manual doesn’t give the pressures, but does state the refrigerant charge should be 14.6 +/- 0.4 oz of R134a. (My manual covers ‘02 to ‘06)

I have an older A/C service manual for late ‘90’s cars, and 250 psig on the high side looks reasonable for R134a refrigerant.

 

What is your high side pressure 135 or 95? You listed both pressures. If 135, your pressures look good based on an ambient air temp of 60 Deg F.



You may be experiencing the same problem I had with my MINI. Connect a Foxwell NT520 Pro scanner (or similar unit), and pull up your evaporator temperature sensor. Yes, the good engineer at MINI actually built a system with a temperature sensor right on the coil. The coil temp should be 32-36 degrees.

If your evap temperature is reading 32-36 degrees, pull up (on the same scanner) your blend air door position. The scanner should show 8 when you select the full cold position, and 100 when you select full hot. In my case, the blend air door would stop at 14 allowing hot air from the heater core to mix with the cold air from the evaporator. I would hold off on filling your system until you find out your coil temp and blend air door position ... making sure the blend air door is working.

https://www.mastercool.com/wp-conten...89660-INST.pdf