I recently purchased a used a/c compressor. I refilled the system with (R-134A) but I am my a/c system is blowing hot air. I was told that I may need to replace the oil in my compressor. The question now is how? I also noticed that the relief valve cover is missing!

 

did you vacuum the system? Did you put any oil in the compressor when you installed it? If you are talking about the little blue or red caps that go on the high and low side fittings, you can get those at any parts store for about a dollar.

 

I did not vaccum out the system, I need help on how to do it! I need to put oil in the compressor, that was my original question!