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Volvo: Another A/V Question, charging station, freon


Question
It is a 1994 850. The A/C stopped working several months ago but just ignored it until now. Basically, it does not turn on at all. I was told to recharge, so I bought one of those recharge kit. Apparently, the instruction says, I must turn on the A/C at full blast while recharging, but of course I cannot do that since it does not work at all. The compressor does not even turn on when I flip the switch. By the way, the switch is fine on the dash, I tested it. I read a little more info online and found out how to bypass the high pressure switch for testing. I did that and walla…, the A/C turns on. I left the bypass on and started charging hoping that with some Freon, I can get the pressure up. After recharging, I can feel the cold air coming and all was good. I go back to remove the bypass, hooked it back up to the pressure switch and the A/C stops working again. Could it be a bad pressure switch? I placed the bypass back on and drove the car around town to see how it does. Of course it works with the bypass, but doesn't seem to be very cold. Also I notice that it will be cold for a few minutes than warm for a few and this goes on and off throughout the drive. When it gets warm, I turn the switch off and then on again and it gets cold again. What is the deal? I truly appreciate your help.

Answer
Randall,
The system hold 1.63 pounds of R134A freon and if it is still low on freon the system will shut down. Because you said that the temp gets warm and cool I would say that the system is still low. The biggest problem with cooling is to get the proper amount in the system, that can only be done with the a charging station. With that you set the machine up to evacuate the system and add the proper charge. You may have used a can of freon that was 14 oz, and lost a bit of the freon while charging and it is still low.
If you do have enough freon in the system the switch could also be bad.