R12 to R134 back to R12? Will there be problems?

[arbowman]

I do not know much about automotive ac systems and how they work. I have a 93 Lexus ES300. I have owned this car for roughly 13 years. The ac worked great for the first 5 years I had the car until until the compressor clutch failed and needed to be replaced. I took the car to a local shop (that I shouldn't have, they were not an ac specific shop) to have this done and when I got it back the ac worked but not nearly as good as it did before. I didn't like them very much so I never went back to ask them what they did exactly and why my ac wasn't working as good. So I just dealt with the poorly performing ac for a few years and IIRC it slowly got worse and worse over time. It has been awhile so I can't remember exactly how bad it had been though. I normally would do a repair like that myself but I do not have the ac recovery and testing equipment to do it correctly.

Then I had some engine problems and parked the car for awhile. I still liked the car so I decided to remove the engine and overhaul it before I put it back on the road. This was a few years after it was sitting. Before I removed the engine I disconnected the ac lines from the compressor but there was no pressure in the lines. I know, I know I should have taken it to an ac shop to have the refrigerant removed safely and eco-friendly but I didn't want to pay to tow it there just for that. It didn't matter anyway, there was nothing in there.

So now that the engine is back in and running perfect, I want to get the ac working again. I did some research and found out that my ac system uses R12 because it is pre-94. I did not know this until now. My options now are to get R12 from ebay and keep my system R12 or convert my system to R134. After doing some research I decided I was going to spend the extra money on the R12 refrigerant and keep my system the same until I read the info below on another forum that concerned me:

"Many things go into changing refrigerants over from R-12 to R-134A.

First of all R-134 requires different seals, both in the compressor, and in places where lines are joined together.

Secondly, the compressor oil must also be changed. The oil used in R-12 is mineral based, and the oil in R-134A is synthetic. The synthetic oil is called "PAG" oil. PAG being short for a 20 letter chemical word I have trouble pronouncing. Using R-134A in a system with mineral oil is creating a nightmare. The system will clog up, and the oil will turn in a syrupy goo, and get into all the small orifices in the entire system. Complete replacement is necessary after that. A quality retrofit will be done by a professional, who will use nitrogen to remove every trace of mineral based oil from the system. The filter drier will be replaced, as well as the orifice tube. The proper oil will be added in the proper level. Just a trace of mineral oil and R-134A together will cause a problem, and the proper cooling will never happen."

Here is my concern after reading this:

The crappy shop that changed my compressor clutch many years ago probably put in R134 after the repair instead of R12 not knowing or caring that it was an R12 car. The shop didn't seem very intelligent so this makes sense. That might be why the ac did not work as well as before, declined over time, and there was no pressure in the system when I eventually disconnected the lines but I am not sure about any of this. My main concern after reading the above info is about the syrupy goo that happens after R134 is put into a R12 system without getting all of the mineral oil out first.

If the shop didn't get all of the old mineral oil out first, am I screwed? Should I even consider putting R12 back in unless I replace everything first? Should I just forget about keeping it a R12 system and convert to R134? What components would I need to replace to convert to R134 the right way? How do I determine if the crappy shop put R12 or R134 back in my system?

How can I determine if my system has the syrupy goo in it now? Does this really happen? What components would I have to replace if it is gooey? What is considered "complete replacement" of the ac system?

Like I said before, I have very little knowledge about ac systems and what each component does. I am mechanically inclined though so replacing parts is no big deal once I know what the part is and does. I don't mind doing whatever has to be done to have a properly working system, but I would like to avoid a HUGE time and labor intensive project. I don't want to spend a fortune either but I am willing to pay what it takes to do it the right way.

Any help, info, advice would be greatly appreciated! Thanks in advance!

[Tim]

Short reply, find a shop that has a refrigerant ana1lyer. Have the refrigerant tested. If R134 & R12. Follow Hecats flushing procedure and replace the oil, drier and o-rings. Charge back with R134a and see how it performs. Or clean the system and charge back with R12 if you can find some.