Thread: Diagnosing a/c system possible freon leak?

02 gp gt 3.8l.

Bought the car in 2015 and the ac never worked. The vents just blow hot air and the compressor clutch never engages. Upon pushing down on the shrader valve there is no hissing or indication of refrigerant in the system. Every once in a while the compressor pulley makes a scraping noise typical of these gm compressors because of the springs. I did apply 12 volts straight to the ac compressor and it kicks on with no odd noises while spinning.

Auto zone here loans vacuum pumps and ac gauges. Should I first try vacuuming the system and see if it holds? What about uv dye and those harbor freight battery powered ac 'sniffers'?

I'd try and vac it down and get a charge in it. Then throw some of the UV dye in as well. Not sure if you'd get the UV dye to show up with an empty system since there is no refrigerant to move it around.

Never tried the Freon sniffers before. Usually my leaks show up with the dye.

Well I vacuumed for 20 mins and it went to -27 psi. Shut the vacuum off. And it remained at like -27 psi for another 20 mins and didn't go anywhere.

So I should maybe vacuum for maybe another 45 mins and let it sit for a hour or so

Well I recharged the system and it's blowing very cold. I did put a bit of dye in the system also.

Drove for an hour and so far it's blowing cold air good

If it held vac for at least 20 min then it's probably a small leak. Mine held for 30min+ and eventually leaked down, but it took a while. If it gets hot again time to start looking for dye.

Look at the bottom of the a/c compressor to see if it is wet with oil (might need a small mirror). If it is wet then the compressor shaft seal is leaking, like mine is. I have to add Freon if the car sits, but if I use everyday the leak is much slower.

I'll have to check tomorrow. Today it's still blowing cold.

If the shaft seal is leaking, will it be easy to see with the dye? Will I have to remove the pulley or anything to see?

If you have the yellow glasses that come with most UV kits it'll be really obvious, trust me. Heck, even in dim light you may be able to see the green tint from the dye.