Air conditioning 101

[jyro]

on o-rings used for AC and most all o-rings you should use whatever oil the o-ring is exposed to, to lubricate the o-ring when installing. For 134a you have to use the green o-rings, I think some are blue too. Tighten the nut or flange all the way down. Never bypass a pressure switch cept maybe for starting a charge or checking to see if a compressor works when the system is out of Freon. Make sure the fans are working and DON'T over charge. If the suction pressure is low and the head pressure is high, clean the orifice tube.

[Gasser64]

Good information all up in hur. Much appreciated

Its just a little confusing cause each time he said he used the black light leak testing fluid, and each time it would still develop a new leak after a while.

[stephen4785]

Good information all up in hur. Much appreciated

Its just a little confusing cause each time he said he used the black light leak testing fluid, and each time it would still develop a new leak after a while.

Probably a mistranslation. The"fluid" is a dye that you put into the system ONCE. You use a black light and yellow glasses to see where the dye has gone/leaked. The dye mixes with the oil and goes completely through the system. Leaks are a problem when it comes to a/c systems. It depends on if the tech coats the o-rings with the right oil, uses the correct o-rings, cleans all of the matting surfaces well and deburs them if needed, and replaces all of the old o-rings depending on their age. The o-rings should be nitrile rubber or hbnr. Nitrile or NBR is supposed to be used in r12 systems. HNBR or hydronated nitrile is rated for r134a and has a higher heat range/longer heat cycle life. Some cheaper o-ring kits are nitrile and the more expensive ones are HNBR. Your mechanic could've skipped something or just used the wrong or cheapest o-rings he could. Like Jyro said your car might have a high pressure problem so it's blowing out seals or have some other issues.
Every mechanic makes mistakes. Iv done jobs and had to fix leaks later but it should'nt need fixing 4 times. Out of curiosity did he convert the system from r12 to r134a?

[Gasser64]

Out of curiosity did he convert the system from r12 to r134a?

No the truck was already retrofitted to 134a when I got it.

[BP]

No the truck was already retrofitted to 134a when I got it.

Most of the early formulas of PAG oil were corrosive to rubber used in older a/c systems. If they didn't install green o-rings when it was converted that'd explain your constant leak problems.

[Gasser64]

Most of the early formulas of PAG oil were corrosive to rubber used in older a/c systems. If they didn't install green o-rings when it was converted that'd explain your constant leak problems.

Could be. However I got a new system installed, and they still seemed to leak. New dryer, new compressor, new... hell I don't know what else. All I know is it was supposed to be a "whole new system" and it came with a warranty which I did have to take full advantage of. I would hope that the new green O-rings would be installed at that time, but I guess some components might not have been replaced? I do know that once he did replace the shrader valve, and once he said it had a big leak where the line connected to the compressor. Maybe I just have bad luck with AC systems, just had to put a new central air on my house earlier this year lol

[shumpertdavid]

People commonly mistake a compressor, receiver drier, and orifice tube / expansion valve as "whole new system". There are still lines, condenser, and evaporator. To replace everything could easily exceed $2000 with most vehicles. It might help if you told us what year, make, model you truck is that's given you so many problems. If it is old enough to us an r4 compressor, they were plagued with leaks, commonly the case seals would leak, the switch port boring in the replacement compressor seem to be a common leak. If it is an 80s truck, the rubber lines weren't designed for r134a and would allow it to leach through. If its a 96 to 2000, the compressor bodies commonly leak.

I've had systems that seemed plagued with problems, and I had others that we did basic compressor / component replacement and they ran trouble free for years.

[BP]

I chased a leak on my truck for two years before figuring out it was the damned high side schraeder valve. I even bought new hoses before figuring out the fitting unscrewed.

[shumpertdavid]

Gm's high side service valve form the mid 90's up has been a common leak. I order 12-15 at a time generally, and will usually recommend replacement during an a\c service. If I don't replace it, 9 times out 10, it will sprew when I remove the high side service connector.

[BP]

Gm's high side service valve form the mid 90's up has been a common leak. I order 12-15 at a time generally, and will usually recommend replacement during an a\c service. If I don't replace it, 9 times out 10, it will sprew when I remove the high side service connector.

That's the rotten bastard! I managed to change it without evacuating the system. Gloves and goggles.

[Gasser64]

People commonly mistake a compressor, receiver drier, and orifice tube / expansion valve as "whole new system". There are still lines, condenser, and evaporator. To replace everything could easily exceed $2000 with most vehicles. It might help if you told us what year, make, model you truck is that's given you so many problems. If it is old enough to us an r4 compressor, they were plagued with leaks, commonly the case seals would leak, the switch port boring in the replacement compressor seem to be a common leak. If it is an 80s truck, the rubber lines weren't designed for r134a and would allow it to leach through. If its a 96 to 2000, the compressor bodies commonly leak.

I've had systems that seemed plagued with problems, and I had others that we did basic compressor / component replacement and they ran trouble free for years.

I remember having to replace the evaporator, as part of the warranty conditions. Its that big aluminum canister looking thing by the firewall, right? Its an 87 sliverado 5.7L TBI truck. Automatic, 2wd if that matters, but probably not.

[shumpertdavid]

That would be the accumulator (receiver drier), the evaporator is the part inside the black box the accumulator is connected to. Should have a R4 compressor (prone to leaks), rubber a/c hoses may not be compatible with R134a (allows R134a to permiate through it), and depending on the quality of the conversion fittings used they could leak as well. They did, however, usually make pretty cold air converted. Suffered some at idle, but that's usually the result of inefficient condensers and evaporators.

[stephen4785]

That would be the accumulator (receiver drier), the evaporator is the part inside the black box the accumulator is connected to. Should have a R4 compressor (prone to leaks), rubber a/c hoses may not be compatible with R134a (allows R134a to permiate through it), and depending on the quality of the conversion fittings used they could leak as well. They did, however, usually make pretty cold air converted. Suffered some at idle, but that's usually the result of inefficient condensers and evaporators.

From his picture I can tell that there the cheap aluminum ones.
Always get the steel ones if you can.