Mixing R-143a PAG and Ester oils

Try the automotive A/C site,

All I know is that if PAG and ester are the same thing, then why did only one of them make my skin itch, and why was only ester recommended for retrofits, at least until about 1995 (I haven't checked since then)?

They certainly, at least back in the nineties, didn't use to be the same thing. I wouldn't be surprised if they are now, though.

--scott

Ester oil works with both R-12 and R-134. PAG is only for R-134. If the oil isn't compatible with the refrigerant, it won't be carried thru the system, will likely collect in the lowest point in the system, and the compressor won't be lubricated.

I don't think PAG and ester will mix but I don't think they'll do anything horrible if present in the same system (except clog it up if there's too much oil). The best idea is to evacuate the system, fix the leak, flush the old oil out & then add the correct amount of both oil & refrigerant. Otherwise, you don't know for sure how much oil you have in the system and too much can adversely affect the operation of the system.

Be careful fooling with A/C systems. It's real easy to screw them up and cause lots of expensive damage. And if you don't know what you're doing you can get hurt or worse. The A/C pros call those little cans with the gauge 'death kits' for a reason (usually it's the death of the A/C system, but if you hook them up wrong it could be yours).

They ARE NOT the same thing. They are chemically different. Ester oil is a slightly poorer lubricant than PAG, but PAG is highly reactive with any trace of chlorine left over from when the system was running R-12. Newer PAG oils labelled "double-end-capped" are chemically stabilized so they won't react with chlorine, and are sold as being fully compatible with R-12. I'm not sure I trust the chemical stabilization process over the long haul, but that's just me. In a retrofitted system, I would always gravitate toward sticking with ester oil, simply because I *know* it won't break down from chlorine contamination. Even though its not as good an oil as PAG I figure non-degraded ester beats the heck out of PAG that's turned to brown grittyt mud due to reaction with chlorine residues from R-12.

The oils are compatible with each other and both are compatible with R-134, so oil circulation won't be the problem. IF there is any problem, it will be one of two things- breakdown of the PAG due to reaction with chlorine, OR a problem I haven't mentioned yet:

ALL R-134a oils (PAG and POE aka 'ester') are extremely hygroscopic and absorb water from the air very quickly. They come with a little water already absorbed, no matter how good the packaging. When you open the cap to add some oil, they absorb a little humidity before you can close it again. Even the "oil charge" cans have traces of water in the oil inside absorbed in the factory where its packaged. Every time you add a little oil to an R-134a system, you ARE adding a little water. Over time continually adding oil to a leaky R-134a system will put in enough water to overwhelm the dessicant in the drier, and when that happens acids will start forming in the system and you'll ultimately have oil breakdown and compressor failure.

Short version: fix the leak.

Thanks for the info.

How will I know when I need to add more oil? I've had to add about 4 ounces of straight refrigerant in the past six months or so but I haven't added any oil yet.

I know how finicky they can be - I had to install a new compressor, expansion valve, drier, high-pressure line, and all of the o-rings on this same system. Huge pain the arse.

I'm more worried I have too little oil in the system because i've been adding straight refrigerant, not the r-134a / oil mixes (I returned that e-z charge bottle I bought). It's only been about 4 ounces in the past six months though.

Why are they called "death kits"? because they often put too much oil in the system or because the gauge is not accurate? or both? I'm been relying on the gauge (keeping it below 25 psi) and watching that sight glass on the drier, which still has bubbles flowing through it.

Both, and that you're only seeing the low side (and often not very accurately). Also, they're often used to convert older R-12 systems to

134 and most people don't do it right...they just let out all the old R-12 (if any's left) and then add the stuff in the cans. Not evacuating and flushing the system and not replacing the drier and not knowing how much oil is in it will often result in a dead system...usually compressor failure. And, if you connect the can to the high pressure side it can explode with dire results.

If you continue to just add gas to the system you have no way of knowing how much (or what kind of) oil is in it (or how much gas is in it either). The only way to know for sure is to start with an empty, flushed, and evacuated system and add known quantities. At least get a decent set of gauges so you can monitor both sides.

Look here

for lots of helpful folks & good advice.

Thanks for the input.

I retrofitted the system about two years ago myself but I had the system evacuated and flushed, then I added r-134a and ester oil (can't remember how much though). So I know it started with the right quantities.

Scott, use your brain for just a quick moment: Does what you just typed make *any* sense at all? No, of course it doesn't -- any more than "Green crayons and dog poo never used to be the same, but it wouldn't surprise me if they are now."

I'm saying that the crap being sold today may not be the same stuff that was in the bottle a decade ago. For all I know, the Crayola may have reformulated their green crayons with dog poo, too. It's NEW AND IMPROVED.

--scott

At best its a guessing game. The last time I tried to estimate how much oil to add over time, I underestimated and wound up with a dry (and seized) compressor in addition to the evaporator core that was leaking in the first place. Thats why I say just fix the leak.