Back to the R12! AC V2 - 07/12/2013

My main project for June-July turned out to be a group buy for A/C systems after being propositioned by multiple people. Seeing as the main channels for getting A/C systems for swapped FDs has dried up considerably over the last year I agreed. The GB was a success overall and wrapped up on August 18th. The original GB thread is located here:

One thing the A/C Group buy did allow me to do was revise my line design and also explore refrigerant options. Of primary interest to me was the possibility of using R12 in a swapped RX7's A/C system. Since the FD was originally designed to use R12, it made sense to me that I would get the coolest A/C if I used a refrigerant that was designed for the factory components still in the A/C loop (primarily the evaporator, but secondly the condenser because even though its an aftermarket unit its still mounted in the factoryish location with approximately the same allowance of airflow).

Since I am the first person to attempt such a feat in a FD (I could find no records of anyone attempting this) I had a lot of legwork to do. On top of that, it is very hard to find information on doing something like this because related questions are generally met with confusion, bad information, discouragement, and/or hostility. I can't really blame the people involved with that kind of feedback because R12 is a very misunderstood refrigerant, and I guess some of the hostility comes from people that HAVE worked hard to get their A/C where it is and having someone discuss the possibility of creating a system that is possibly better somehow makes them them mad? ;)

All that just fueled the fire though as it was an interesting and fairly unique idea to explore

One of the first things I wanted to find out was if the LS1 compressor is compatible with R12 since there was no reason in chasing after R12 if it was incompatible with the seals used our modern compressor. I found references to the V5 Delphi compressor in this document (which I believe is what the LS1 came with from the factory)
It mentioned the V5 compressor as being "compatible with R-12 and R-134a systems." So I took that as a green light and continued.


The second hurdle to overcome was the availability of R12. I have a long history with R12, but there is a MOUNTAIN of bad information on the internet, so for someone who doesn't know any better its easy to see why people end up thinking that there is only a few lbs of the stuff still known to exist and it sells for $200 an ounce! lol!

Three points that most people don't realize is that when R12 was banned, it only banned NEW production of R12. Existing R12 is still legal although regulated. 2nd, from memory, R12 only got banned in the USA. While that's a big chunk of the market, other places in the world still have it and manufacture it. 3rd, existing US made R12 can be reclaimed, recycled, and resold.

So, that makes R12 sound a little more obtainable right??

The problem is that it IS still very much regulated and it is hard to get without knowing the correct channels. I started by getting EPA 609 certified on this website for $20. The EPA 609 certification basically gave me free range to work on automotive A/C systems with R12 and purchase R12. With the EPA certification it was easy for me to purchase 28oz or R12 for right at $50 on eBay.

The third hurdle was the actual lines. R12 uses different style service ports, so my lines would have to be remade. The GB helped me out with this since I had everything in stock I needed to rebuild my lines with the correct service ports. Afterwards I sold my existing lines to a member here at a discounted price.

The fourth hurdle was addressing the fact that R12 uses a different type of oil than R134a. R134a uses PAG oil whereas R12 uses Mineral oil. This is important because you can't mix the two together which means I would be looking at flushing EVERYTHING in the A/C loop. Since I replaced my lines they were new and wouldn't have to be flushed, so for me this meant flushing my evaporator and condenser. For my compressor I just drained all the oil I could by unbolting it, turning it upside down and turning its drive wheel. I continued by flushing everything out with FJC KwickFlush and compressed air. Afterwards I oiled the system with ~6oz of Ester oil. I ended up going with Ester oil since it's supposed to be compatible with with PAG and Mineral oils, so if traces of PAG were still around in my compressor it shouldn't cause too big of a problem.

The 5th hurdle ended up not being a hurdle at all. R12 runs at a slightly lower pressure than R134a. Since my PCM uses a GM pressure switch that is designed for R134a I had concerns that it wouldn't work well with R12. Well, like I said it turned out to be a non issue as it was perfectly happy to let my compressor cycle when I commanded it to.

Results = ICE Cold AC