I need help with my 1993 grand cheokee ac. I think I need to charge the system, just not sure how. When the unit is on ,the compressor only runs for 15 to 20 seconds at a time, then off for about the same. please help.

 

That does sound like a low charge. 93 will provably need r-12 which is unobtabium nowadays. You can convert to r134a though, just make sure to do it right.

 

If you don't now how the system works don't screw with it. Take it to a shop and have a pro repair it correctly. You will save money and have a lot less headaches.

 

My 93 use 134, buy refill at ebay.

 

R134 is a bigger conversion than the cans at Walmart make it out to be. TO do it correctly requires disassembling the entire system, flushing, new receiver/drier, all new o-rings for use with r134, ideally a new compressor for use with the higher pressure refrigerent, etc.

That said, there's a product out there called Freeze 12, meant as a R12 replacement. You can buy off Amazon if not sold locally, though your local automotive A/C supplier should stock it. Works at similar pressures as R12 so it won't kill your existing hardware like R134 can, and cools better at these lower pressures.

In either case, if you're serious about doing your own a/c work, which isn't difficult but does require a good set of manifold guages (and adapters for your R12 system) and a fundamental understanding of how a/c systems work, how high/low side pressures relate to general state of the system and its individual components, etc.

I mean, I'm just a lowly computer nerd and I can make my a/c blow cold again, so don't feel too daunted by the task.