A/C Dryer Relief valve?

Is there such a thing? I think I over filled my A/C and it started making loud farting like sound (thought it was me but I could tell it was in front!). Looked around and found oil discharged from the bottom of the dryer.

The pressure was around 45 PSI. I didn't think that was out of line.

Oh yeah, it was converted from R12.

Most cars have the relief valve on the compressor. And yes this sounds like what happened. have the system vacced down and recharged with the proper weight of freon. Always go by weight and not just gauge pressure. also keep in mind when converting from R12 to R134 you only need approx. %80-%85 percent of the R12 charge...Now just hope doing this didn't didn't create any new leaks...good luck!!!

How do I determine weight requirement for r12?

sjx40250 said:

How do I determine weight requirement for r12?

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It is on a sticker under the hood. If it's been removed, chiltons book, etc. should have it. Use a a/c scale or machine so you know you have the right amount in the system. Remember to use less freon if converting to R134

Thanks for your response! Any ideas on how to evac at home? Its R134, do I still need certification and a license to evac?

You don't need a license for 134 but without a vacuum pump and a scale, you might be better of finding a shop that will charge it up for you for a couple of bucks. You can probably rent the equipment, but it might cost as much as paying someone in the first place. Ask around...

To do it right you need a good vacuum pump.

What is the history of the AC system? You might not need to drain it if you simply overfilled it. But from the sound of it, the HP cutoff switch on the filter dryer needs replacing which means pulling a vacuum.

Yes, there is a high pressure relief valve on the bottom of the filter/dryer. If the high pressure switch fails to turn off the clutch and unload the AC compressor then the High pressure side pressure can get too high if the electric condensor/radiator fan is not running, or if the expansion valve plugs up, or if there is too much refrigerant added to the system or any combination of the three. The pressure relief valve is there for safety, anti explosion protection back up to the electric HP cutoff switch.