Having recently replaced condensers, dryer, O rings and having the system vac'd and re-gassed my 996 has been blowing ice cold air until a couple of days back. It was blowing cold Monday morning but getting back into the car that evening was blowing just warm/hot air. The rest of the week has been fine am & pm until today. Took a 30 mile trip today blowing ice cold then suddenly you can smell the air change and blow outside temp air. It's been doing this on and off for the rest of the day. I'm puzzled and can only assume the following A: the pump/compressor has a loose wire or similar and is kicking in and then switching off or B: they didn't put enough gas in and it's cold for a while but after running for a while it doesn't have enough gas to keep up the ice cold air. Heading home from the grocery store today the air was warm but without touching any controls suddenly blew cold air again.
Please help

 

The factory repair manual has a chart that lists for every component in the A/C system a corresponding amount of compressor oil this component takes with it, is lost, when the component is replaced with a new one.

Thus the system is evacuated and the amount of oil removed is noted.

The amount of oil lost due to components being replaced is also noted, tallied, and when the system is put back together and after it has been kept under very low pressure, a vacuum, for IIRC the time has been upped from an hour but I don't remember the new time, with no leak sign, then the proper amount (weight I think) of refrigerant is returned to the system along with the proper amount of compressor oil -- with if the amount pulled from the system down from what it should be made up with new oil.

The car is then road tested to ensure the A/C works properly.

Or theA/C system can be tested in the service bay. The factory repair manual has a chart for ambient temperature vs. center vent A/C temperature at some engine speed above idle and with the A/C controls set to max cool.

My guess is the system was not properly filled with refrigerant (and possibly compressor oil) or there is a leak anb the system is low on refrigerant.


Oh, just an afterthought, but be sure the radiator fans both come on when the A/C is turned on. No need to run the system very long, just long enough to confirm the fans come on when they are supposed to.

 

Thanks Macster, cars booked in for Saturday. A phone call to my Indy said pretty much the same as you, adding it's likely they filled to 400 or so rather than fill to maximum as the car will still function anf blow cold and they save $$s on refrigerant. I'll update further come Saturday

 

Could be the compressor clutch too