I bought a 1994 coupe about a month ago. The guy I bought it from said he just replaced the compressor. Well I have been driving it for the past few weeks and it didnt seem to be cooling as I thought it should. So I went and bought a can of freon with a gauge on it I stuck the hose with the quick dissconnect on it with the gauge and it was reading 35 psi .The instructions said safe pressure was 25 to 45 psi so i thought I could put a little freon in it. I started adding freon keeping an eye on the gauge I stopped when I reached 45 psi. The next morning i started up and turned the air on and the compressor sounded like it was cutting on a off as if it was low of freon. Today i drove it to town and turned the air on when I started home and the compressor started the same thing. when I got home I checked the preesure and where I was getting 45 psi I was now getting 135 psi and the compressor was sort of slow engaging and would not stay engaged long at a time so I thought I had to much pressure and decided to drain some of the freon manually. Igot it down to 45 psi but the compressor still engages slow and sort of sounds like the belt is slipping but it,s not.When engages it will runbut the lines dont get really cold like they should. I really need some help before i mess somthing up.

 

Take it to a shop that handles alot of auto A/C, ask around to find someone with a good reputation. without having any experience on A/C your shooting in the dark trying to get the chage correct.

 

I think youre right.

 

Small A/C systems such as those found in automobiles have a narrow tollorance for being over or under charged (critical charge), also whenever the refrigeration system is opened to the atmosphere contaminants will enter and if not evacuated well will cause issues such as high head pressure ( high pressure switch cycling ) and/or poor cooling even if the gage shows proper pressure. You said the compressor was replaced, do you know the reason and if any other components were changed at that time such as the metering orifice or any filter/dryer in the system, you may have a restriction in the refer system due to compressor failure in the past.

 

All quite true. And adding refrigerant w/o a thorough understanding and analysis of high and low side pressure readings for a given ambient temperature is a dangerous crap-shoot. Excessive refrigerant can trash a compressor in short order.