Last fall I spent $1,000 getting my a/c updated to R-143a. New compressor, accumulator, seals, orifice tube etc and it worked beautifully for about 3 weeks, then it suddenly stopped working. Now it won't hold pressure at all and there is no sign of a leak anywhere. It has been professionally checked with a black light by the mechanic who did the work for me, twice. No luck finding it.

The system had not worked since about 2001 before I had it rebuilt. If anyone here knows of a component that may have silently failed or if there is a specific place that I should start looking to find this leak please reply. Thank you. It's hot outside.

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Im guessing, the AC mechanic is looking in the wrong location. Im thinking its a pin hole in the Condenser or AC line in front of the radiator, called the air conditioning condenser (looks like a radiator). A small stone could have easily made a pin hole up front in the Condencer. Try again with the UV light up front or in between.

[This message has been edited by James Bond 007 (edited 07-19-2013).]

I'll have a look there. Thank you for the reply.

It will be a few days before I can get back home to look for it but that will give me time to get some recommendations about where to look.

Does the system hold Vacuum? I would check all the connection points. When you convert to 134a, you have to change all the washers and seals because the particles are smaller than R12. Also, have him use a chemical detector, and not a black light. Black light only works of the Freon is dyed, and if its all leaked out you won't be able to see it.

Have him check the hoses under the car that run from the front to the back. That's where I found my leak. The dye lit up like a Christmas tree when we looked underneath.

If the system isn't entirely flat (i.e. no refrigerant pressure at all) you can use an electronic "sniffer" to at least narrow the search. Systems that have been sitting discharged for a long time, especially if they have been open to the air even momentarily, are subject to internal corrosion due to moisture in the refrigerant. Besides the condenser, already mentioned, use a sniffer to check the evaporator coil (located in the heater box). The shaft seal at the pulley end of the compressor is the common location of a hidden leak. Be sure to check all tube connections with the sniffer, too, as well as the hoses, hose crimps, and end fittings. Finding the problem is just a slow process of elimination. Since you replaced most of the system less than a year ago, the condenser, evaporator, tubes, and hoses should probably be the first places to look.

There is no need to replace the O-rings in connections that aren't leaking. That is the recommendation of both GM and the EPA. If it ain't broke, don't fix it. Of course, if you open a fitting you should always replace the old O-ring with a fresh new one of the correct size and type.


Edit: Always lubricate new O-rings with mineral oil, regardless of refrigerant type in use, before reassembly. Don't use PAG or ester oil to lubricate O-rings ... only mineral oil.

[This message has been edited by Marvin McInnis (edited 07-24-2013).]

I purchased a black light in the form of a small flashlight off ebay and it worked wonders. Once the dye was added finding the leak was easy however, the darker it is when you perform the check the better. On a previously sealed and leak free system I'd highly suspect the wrong o-ring was used somewhere. As for the evaporator, since the A/C worked for a while I'd expect you to be able to detect a leak in it by focusing on the condensation drain area which should have dye mixed in with it and therefore show a trail in that area.

On a different note, I believe the quantity of R134 used should probably take into account your environment, so far the rule seems to be 80% of the R12 volume as a rough estimate, but I believe the hotter and more humid the climate the more you should consider a little less. I had excellent cooling on two cans of 134 in GA, but after a repair in FL and a refill to the 80% quantity (3 cans) I noticed cooling onset is a little sluggish within limits on the gauges, however, the system pressure runs a little higher and when humidity goes up it gets worse as the high pressure switch activated recently at idle and I've noticed the engine load is a bit greater.

Thanks for the recommendations. Die has been added. I'll check around to see what I can find out today. I will be purchasing a black lit of my own to use if I can't find the leak today.