HOW TO: Charging your A/C air conditioner conditioning system at home.


Yes I do own a turbo
Dec 10, 2005
Scott, La
This is just as a note for those that say that r-134a isn't as cold as R-12.
My converted 89 still blew 34 deg air out the vent sitting at idle in a parking lot after sitting at idle for about 45 mins today in the sun with 99 degree reported temp.
It may require more more power to run the compressor, I don't know, but it does blow very cold air.
If your system does not blow cold enough I recommend a few things
1) make sure you bled the line between the can and the manifold (with shrader valve and can upside down) with every can
2) your fans are operating 100%
3) you have no restrictions in your system.


New Member
Aug 25, 2005
Popemobile had a very good conversion.

The best conversions to R134a occur when it is converted from a "working" R12 system.

Vent temp readings are based on ambient heat/humidity. There's a number of charts on the web that describe this.

A few notes from my experience.
- A good R134a conversion can yield an average a 45-50F vent temp. Not great, but still helpful on a hot and/or humid day.
- Condenser heat exchange is important, as Popemobile notes that the fans need to work 100%.
- Vacuuum testing. It is best to hold the vacuum for at least 30 minutes to determine if there are any leaks.
- Pressure testing - usually done with Nitrogen, determines if there are any pressure leaks. Usually pressurized to 180psi, then re-checked after 30 minutes. One usually need to do this at a trucking AC shop, as standard automotive AC places usually do not do this.
- Trying to convert or fix an unknown condition AC system can be a money pit.

And lastly, the R134a is not as efficient myth. R134a molecules are smaller, and exchange heat at the evaporator at a faster rate than R12. Which is good. Though, since smaller, take extra pressure and heat exchange at the condenser to return to a liquid. The later creates a performance obstacle with a car originally designed for R12.

To get the proper balance, the two main components that achieve a far more successful R134a conversion is an improved condenser and a compressor that is designed for R134a.

I created a R134a conversion kit for the MK2 community in 2006, which included a both. A high performance AC condenser, and a far superior R134a compressor (better and cheaper than a NipponDenso). (And a bunch of other improvement parts). End results were great. Comparing two of my MK2's, one with R12 and the other with R134a, the R134a cools faster and reaches a lower vent temp.
Someone might have already said this, but there is too much to read through. But what i do is go to a shop and have them evac the system for me. It is basically like they are doing the regular A/c system stuff, but they just don't put anything back into the system. I did this last time in exchange for a case of beer . My next door neighbor worked for firestone :) Also, i use a Canadian R12 chemical. It works just like r12, but contains no cfc's. It is great stuff and costs about 10 bucks a lb, instead of about 50. It is totally legal. I bought 12 cans a few years ago. Because it is so cheap, you can afford to just top off a leaky system once a year :)
Mowgli87;1868622 said:
Bumping an old thread for some more info. Found the Toyota TSB for retrofitting R-12 AC systems with R-134a. Figured it would be right at home in this thread.

I am not sure if you missed it, but my last post mentioned modern R-12 refridgerant. I seriously do not recommend using R-134a on your supra. It is a horrible refridgerant, r-12 is MUCH cooler. There are quite a few alternatives that do not contain CFCs, yet work just like R-12 and will not destory your A/C system like R-134a will. I have 2 cases of the R-12 stuff from canada. I ran it on my first supra, but my last one was totaled before i was able to fill it. I am now driving a 1999 3000GT VR4 until i can get a MKIV supra. I dont think i will use the conversion kits i have :(


New Member
Feb 19, 2006
Sunny SD
awesome right up! Thanks so much for this. I finally have ice cold AC after owning my car for 13 years. What I feel did the trick was the vacuum process. One thing I would like is if you would to be a little more specific on your steps as far as closing/opening valves. Could you go into more detail as far as specifying between the manifold valves and the coupler valves? I think that would really help out. whenever you said to open or close the valve I did both the coupler and manifold just to be safe. Thanks again!