I have an older vehicle that has AC, but it needs a recharge. It uses the older R12 refrigerant and it is very expensive and can be difficult to locate as it is not made in the US anymore. How do I convert it over to cheaper newer R134a? Can this be done without replacing the AC compressor?

  • I haven't done this, but a little surfing finds: ehow.com/how_6616048_convert-r12-r134a-system.html
    – Peter K.
    Commented Mar 12, 2011 at 19:28
  • It might depend on the vehicle. Can you be more specific? For instance, my mechanic told me that my 1992 Volvo 940 would need a new evaporator and condensor in order to use R134a. Commented Mar 14, 2011 at 16:05

3 Answers 3


Checkout the Auto AC board at AC Source

There are some good people on there.

Don's right. You do need to flush the old oil out of the system because they don't mix. Also it's difficult to flush the compressor so odds are it will not last if you don't replace it. The best thing to do is change the compressor out if its older at the same time, replacing all the o-rings too. R134 operates at higher pressures and it won't be as efficient, so you have to be careful not to overcharge. Older condensors designed for R12 might not cut it.


I have done it before. I just replaced all the seals and o-rings, cleaned out all of the old oil and then refilled with r-134a. That's about it. I did it on an '86 Volvo 740 and it worked really well.


Probably a decade ago, I had a mechanic I trust do a conversion from R12 to R134 on a 1977 Cadillac I own. The conversion was necessary since the compressor locked up. He replaced the compressor, dryer, orifice tube, flushed the system. I queried him why he didn't replace the lines and o-rings. He replied it was not necessary. He said using the replacement old style compressor and condenser, it would not get as cold as it originally would, but it would be fine. Ten years later this seems to be the case. I haven't had a day in Georgia or Ohio where I felt like the A/C was insufficient.

On Grassroots Motorsports, I like this short list of things to do:


  1. Borrow w/deposit vacuum pump from your FLAPS
  2. Buy adjustable orifice tube ~30
  3. Buy new dryer/accumulator
  4. Buy oil and R134a from FLAPS
  5. Drain old oil from compressor
  6. Replace the accumulator/orifice tube
  7. Vacuum down for an hour
  8. Let it sit and make sure there are no further leaks
  9. Charge up with R134a.

I have an RV that I plan to do this conversion on. It was down a bit, I have recharged it and tested it with R12a (propane). I have found the leak on the receiver. I plan on replacing the compressor just so I know all the R12 oil is gone. I believe I can successfully flush the rest of the system.

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