87 Deville AC Issues

[waterzap]

Have a bit of a problem with the AC. F48, low refrigerant comes up in my 87 Deville. Yellow light in dash. When I switch off the AC, the light goes off. Blows cold air. Light also does not come on when I am on the highway. Air is cold and all is fine.

I measured the charge, and the compressor keeps on cycling on and off. As soon as the pressure drops to around 32 psi, the compressor switches off, and I get static pressure, which is of course much higher. Then a few second later, switches on again, pressure drops, switches off at 32. I get good cold air. Got a thermometer in the dash vents, and temp does go down to around 42

I don’t just want to add more refrigerant. 32 is fine for R12. Just ordered a new low pressure sensor. I did not have an adapter for the high side, as the car is still on R12. Any other ideas?

[KHE]

Usually, when the system says it is low on refrigerant, it is low on refrigerant. Sounds like the refrigerant level is low enough to the threshold that it trips the code. What are the readings on the high pressure side?

[waterzap]

Didnt get high side readings. Didnt have the adapter for my hoses. Ill get one online, see what that says. The low side just screws in, the high side has a quick connect connector, but smaller than the R134 hoses. Guess could get adapter somewhere.