The low side is the only one the canister will fit on. Above the passage side headlight

 

That is correct.

Low side is suction side. It should not be building pressure. High side is restricted by the orifice tube. It only allows so much to flow. (and expand..... thus, getting REALLY cold) If low side pressure is going up while the compressor is running, I suspect you have some other problem in there as well.

 

Alright so maybe I was wrong. Today I filled up the wife's car with one of them cans of freon. When I was done I hooked it back up to mine. The pressure builds when the clutch is off but goes gown when it's on. I'll have to get another can and top her off

 

That's the way it is supposed to work.