Alternate refrigerants - a cautionary tale
 

What follows is a fairly lengthy letter submitted today by a lister on the mbz.org diesel list. Since the weather's warming up, and there's been some discussion of the refrigerant in question, I'm submitting this as a word to the wise. While the refrigerant in question is Duracool, the same potential exists with other hydrocarbon refrigerants.
Hopefully this gentleman's engine isn't damaged, but his follow up emails weren't promising. Just so I'm clear what follows IS NOT FROM ME, so there's no need to respond to his questions. This is for your information only.

As most of you probably know, I use Duracool 12a as my refridgerant in my car, and I really like the cooling properties. However, I had been having a slight leak on my low-pressure switch that attaches to the condenser-side of the accumulator. Well, today I hooked up my gauges and wanted to add some to it. The recommended low-side pressure is 40 PSI at 1500 RPM. Well, by gauges were leaking pretty badly (actually the hoses, but you know what I mean), so I scraped them, and put in a can directly. It still needed the amount anyway. Well, upon doing so, the seal were the low-pressure switch is blew, creating a huge misting cloud of Duracool 12a. This is where it gets interesting. I immediatly disconnected the can from the manifold, and suddenly the engine's RPM went through the roof! Soot was blowing everywhere out of my exhaust, and the governor was the only thing holding it down, I think... and hope. I ran to the ignition and pulled the key out, but it continued to run, so I hit the manual kill, and it still ran. Finally, after an eternal 5 seconds or so, it died. I was completely confused as to what might have caused it, and then I realized what happened. Duracool 12a is a mix of two hydrocarbons: isobutane and isopropane. Well, seeing as the accumulator is right by the air intake, those fumes got sucked right in, sending the engine speed sky-high. I cut off the supply of diesel, and it continued to run on the Duracool!!!! Scared the crap out of me!!!! So, after a while, I went out and tried to start it again (all of the Duracool was long gone by this time), and it took a few tries.
Once it finally started (crappy firing, took a lot of persistence) the idle was INCREDIBLY rough and down to about 600 RPM from 750 RPM. I reved it some, thinking that maybe when it took off it had dislodged a lot of soot. Well, a lot of soot came out, but smoke too... and quite a bit.

So what have I done? It still idles just as rough. Have I blown an internal seal or something? Please, tell me anything. I am worried to death here and really need some guidance. Thanks in advance, and be careful of those low-pressure switches.

The problem you had is one that oil well firefighters also have when running their Diesels around a well blowout. The natural gas will overrev the engine and there's really nothing the governor can do about it. You'd need a CO2 fire extinguisher to kill the engine.

Sorry, can't help you with your problem.

Sholin

Although I feel sorry for this guy, this was all because he wanted to save a few bucks on refrigerant.

R12 is STILL available, although expensive, it is what that air conditioner was designed to use. You don't have to replace R12 unless it leaks out. If it leaks out, then something has to be fixed to prevent further leakage. That SOMETHING typically is much more expensive than the R12. Why not spend a few more bucks and put in the R12? You will be safer, your engine will be safer and you will be comfortable while driving. If you have done a good repair job, you very well could be comfortable for the life of the car.

I remember my Grand Dad always saying about my Dad that he "spent dollars to pinch pennies." This definitely applies here.

If you drive a car that originally came with R12, most others who do will not be driving it for long. This means the demand should go down, thus the price should continue to go down. Just use the right stuff, be safe, comfortable and happy.

Good luck,

Larry,

Please keep in mind the possibility that he was switching back from R134a. Its said that R134a does not cool as well in cars not designed to run it. Its also said that genuine R12 will do very nasty things when mixed with the R134a PAE/PAG oils - such as eating holes in A/C parts when hydrochloric or hydrofloric acids are formed.

It is MOISTURE that sets up an acid when mixed with R12 or R134a either one. If you are changing refrigerant and oil, one should THOROUGHLY flush the oil out of the system or you are BEGGING for problems.

Actually, I think one or more of the alternate refrigerants are blends of R12 and R134a.

Have a great day,

Larry,

This is what I've got from someone who knows refrigerant:
Maybe he is wrong?

Thanks,

I'm with Larry on this one. Even R12 is cheap compared to the rest of the A/C parts that you're going to contaminate with alternate refrigerants. And the risks involved with flammable refrigerants are just not worth the few bucks saved.

As for reverse converting and acid production, that's why you flush thoroughly and vacuum for a long time.

I have read many times and many places that you should NEVER use PAG in a converted system. You may have uncovered the reason for this. I assumed it was that the PAG and mineral oil together would coagulate, but your acid theory has more logic to it.

This theory floats only with PAG oil, however. It has been accepted for some time that Ester is the oil of choice in a converted system. I don't think this has much to do with the original post however. The issue was the flammability of the refrigerant.

Summary: Use PAG in systems that came from the factory with R134a, use Ester in systems that have been converted from R12 to R134a (or specified by the orignal mfg,) and use mineral oil in an R12 system. In addition to those three simple rules, always thoroughly flush the system EVERYWHERE to remove the previous oil whenever conversion is performed.

Have a great day,

Larry,

I agree with your comments about when to use PAG and ester oil. However, I have read that some components such as compressors and condensers cannot be flushed and must be replaced. This added expense leaves some searching for a safer conversion. I beleve some do exist, and AutoFreeze may be one of them. I'm not a big fan of propane based system. Always replace the drier when the system is opened to the environment.

Regards,