Dan: I was also in the dark about a/c service, but had a neighbor that came down the alley with the same tools he used on house a/c systems, and charged up my system and tested for leaks. The a/c in my wagon has run for years w/o issues.
Others jump in here if you find any issues with my logic. The system has freon that changes state, gas to liquid in the compressor, and then the freon travels to the evaporater where it expands to a gas again and transfers the heat from the air around the coils to the freon which returns to the condenser in front of the radiator. The condenser cools the freon and returns it to wthe compresser .....
So find the leak......uaually a loose fitting or dried up and cracking o-ring, sometimes a bad seal in the compressor....also in the freon is an amount of oil that lubricates the compressor, and can leak out of the same leakpoint as the freon.
So look for fittings with oily dirt collected on them. Don't forget to look at the dryer, the part that's vertical about 2.5" dia.
If they open the system at all this needs to be replaced as it can hold only a small amount of water that evacuating the system leaves behind. When empty the tech will pull a negative pressure on the system and it should hold the pressure, or this will confirm your leak. The freon is evacuated so it can be recycled and not just dumped into the atmosphere. It also lets the proper measured amount of coolant and oil to be placed in the system. To me it is training I have not recieved, just observed the techs when they work on it. One more thing is I have seen them use a leak detector tool that will indicate that freon is present outside of the system.
Good luck Dan.
