Testing AC

Can someone please tell me if I need to put 2 cans of r134a with dye into the system to check for leaks, or will one do the job? The car was taken to a shop last year and dye put in to check for leaks but my son failed to take it back in. The a/c was gone after about 6 weeks. He wants to do the test himself to try and save money. Thanks in advance

It would help to post what year and model GP you have.

Regardless of whether you use one or two cans of R134 with dye the system refrigerant charge should be brought up to specs or a proper charge based on the temperature and humidity so it is hard to say whether one or two cans would be correct. Hopefully you have the right equipment to do the job and that includes A/C manifold pressure gauges to check the low and high side pressures and properly dispense the refrigerant.

It is a GP 3.1 2001. He has the pressure gauges. I presume he puts the charge in until the correct pressures are reached according to the outside temperature at the time. I guess this answers my query. Thanks for your help.