AC recharge on 76 K5????

[Chalet 170]

I have a 76 K5. Looks like is has been converted to 134a.
There is a black canister looking thing with a port on it, and a hose coming from the box on the firewall that runs to the compressor, the hose also has a port. My question is: which one do I check the pressure on, and which do I use to recharge the system?
Sorry about the dumb question, just don't want to pay someone for something I can do myself for less.

TIA
Doug

 

[95 Silverado]

if you are using the single line type charger, found in most universal type recharge kits. they must use the low side of the system. on the compressor you will have two lines, a large one that runs back to the evaporator/heater box and a smaller diameter one that goes to the condensor in front of the radiator. the small line is the high side of the system, do not hook up to these fittings anywhere along it's path back to the evaporator box, when operating these pressures are too high for the tester. you must hook to the larger diameter hose side of the system, this is the suction side, where it will draw in the freon. most of these fittings are different sizes to prevent a mistake.if you're not sure, don't put safety aside to save a few dollars as freon under pressure can be dangerous.