Hello everyone newbie here very helpful info listed thank you. Last year disassembled and flushed AC system, new compressor, orifice tube, accumulator. Vacuum could not hold very slow leak. Couldn't find leak with sniffer or UV dye. Recharged AC had great air and took to mechanic and they vacuumed and recharged did not find leak. Had good AC all summer. Stored winter. This spring no air. Should I refill AC using old accumulator and drive to get UV dye to leak out - how long? Will it harm system with old accumulator running? Don't want to kill compressor. Trying to be a DIY and save cash. New mechanic? These guys are honest and very fair. Trying to understand AC but leak is driving me nuts! Great car. Please help.

1 Answer 1


You'd have to weigh the cost(s) and make your own decision.

New compressor rules out shaft seal, which was my first guess. But technically, a new compressor always commands a new receiver-dryer. There are some specially treated PAG oils that can help small leaks, but require at least a partial charge to inject. If it's a new "accumulator" as you call it, it should be fine to continue running it. but I would certainly double check every connection you had to loosen in order to replace those components.

Also, did you sniff of examine the valve cores on both high and low fittings? Another notorious spot for the "impossible-to-find" small leak.

And no matter how silly it sounds, try your UV search at night. (One neighbor is still quite suspicious of me, albiet this practice admittedly not the only reason...)

  • Thank you Steve. I am learning to use the CPS Refrigerant Leak Detector - LS790B and will recheck the system again. They claim this leak detector is calibrated to detect a leak rate of better than 0.25 oz/yr (7g/yr) of HFC. Is that sensitive enough to detect very slow leaks? What do you use to clean old UV dye from system to recheck for leaks? Should I charge AC to max and drive to force UV dye to show? What do consider the most effective for leak detection, UV dye or Sniffer? I will do a UV search at night, great idea. Sorry for all the questions but I AM going to find this leak! Commented May 28, 2017 at 10:47
  • 1
    You lost the entire charge - probably 1500 to 3000 grams over the winter, so a mere 7g/year leak rate is two magnitudes more sensitive than you would need in theory. Leave the old UV dye in there; it's hurting nothing. Both UV and sniffer have their value. I prefer the UV because it's beyond denial, and simple even when operating. Sniffers sometimes are difficult to get in a zone of detection, and the air needs to be very still as well - no wind or overhead fans. Good luck; patience and diligence will be your weapons.
    – SteveRacer
    Commented May 30, 2017 at 0:15
  • Sorry, didn't word correctly about UV dye. I meant to say how do you clean residue UV dye traces on outside fittings and parts from previous leaks so that you can start fresh for inspection? What removes and dissolves it best to wipe it off everything? Commented May 30, 2017 at 11:20
  • 1
    "Brake clean" (the illegal in CA/NJ) CRC red can. Ever-nifty Tetrachloroethylene, which also kills bugs, rodents, and most humans. Instantly flashes to toxic vapor; added benefit of creating phosgene style chemical weapon if exposed to UV welding radiation. Four decades using chlorinated brake cleaner explains some, but not all, of my strange behavior. Seriously, anything that surfacts a PAG oil (which transports dye) like a simple detergent should work. Besides, you can just leave it. I thought the issue is you aren't seeing any UV dye traces, and now you worry about how to wash it off??
    – SteveRacer
    Commented May 31, 2017 at 3:53
  • Hi Steve. Cleaned up previous UV dye from old rebuilt compressor that leaked using detergent. Used new UV light that is more powerful. I found the leak at the new compressor. One of the transducer pressure switches (correct name for switch?) is leaking around the port. Going to try replacing O ring with compressor on car. I have strange behavior too like crawling around under a car trying to fix something that probably should have gone to a professional in the first place. I played in lead gasoline as a kid cleaning bikes and later cars plus everything else. Talk about toxic. Commented Jun 6, 2017 at 9:42

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .