Originally Posted by
Jonathan
I would not suggest forcing 12v onto the compressor to actually get it to run. If indeed it is low on refrigerant, running the compressor this way will likely lead to damaging the unit.
To test whether your system is not coming on due to a low pressure problem, jumper the low pressure switch up at the front right wheel well and listen for the compressor clutch to "clack" in. Do this without the engine running, i.e. ignition key turned to accessories only. If the clutch clacks in while the low pressure switch is jumpered, then it is one of two things:
1.) your refrigerant level is low (likely)
2.) the low pressure switch itself is bad (less likely)
If you do the test and find the clutch clacks in, you then should be measuring the refrigerant pressure with gauges hooked up to the proper ports. Or measure the pressures right away.
Again, I recommend not forcing the system to run with low refrigerant.
As for getting it topped up with R12 in the US, someone else can tell you about that. I think it got banned because it was bad for the ozone layer. Converting to R134 or whatever could be expensive, yes. You could also add a can or two of the R12 equivalent stuff and see how it goes.