R12 to R134a A/C conversion: What's your experience with this?

[Road_Runner]

My 73 is in the shop getting the A/C fixed and due to all of the parts including the compressor being original the shop owner doesn't want to try to convert it without putting on a rebuilt compressor & drier first.  He's also going to rebuild the hoses.  Any of you done this conversion?  What if any are the pitfalls to watch out for?  Does it work as good now as before?  I'm going to go this route regardless but knowing about any gotcha's ahead of time would be nice.

Thanks, Jim

[purple1]

New dryer would be a must. The rebuilt compressor may not be needed if your compressor is good. Just drain all the old oil out of it and fill it with the new oil. Rubber hoses need replaced and all the O-rings in the system should be replaced as well, the old rubber will degrade with the 134a. Running a flush though the system would also be a good idea. The 134a will not cool as much as R12, but you can get it to cool very well when charged correctly.

[burdar]

We did quite a few back when I was a mechanic.  We'd pull the comp. and drain the oil...replace the O-rings and re-fill with the new oil.  We never had to replace any rubber lines but that was on newer cars.  30 year old A/C lines should be replaced anyway.

If I remember correctly, 134A will produce higher system pressures too so everything needs to be in good shape. 

[Supercuda]

You need to completely drain the compressor of old oil. Best bet is to replace with a comp. that is built for R-134 already. You can do this with the old V-2 compressor. Modern axial compressors are better, but don't look right. New hoses with proper material, a new dryer, and a VERY good flush of any components not being replaced, is required. The oils used in R-12 systems are not compatible with the new stuff, and acids will form, ruining the system in short order. Also stay away from any refrigerant blends, as these will let you down.

[Road_Runner]

Thanks guys, I've ordered a rebuilt compressor & a new drier.  The owner said they would make new hoses for it and as good as they have done me on everything else I'll bet he plans to do all of what you've outlined above, but at least now I know what to ask about.

Thanks again, Jim

[Moparal]

Dryers do not really like 134A and have a tendency to expire quicker, the accumulator and orifice filter does a better job and is still used today. Also head pressure is quite a bit more, so never run the a/c when under a load at higher rpm's or you will experience a compressor rod failure.  Just a guess, but maybe 20% actually last endurance wise. But are older granny driven on short drives. If it were me, I'd just spring for R12 make sure it is sealed and holds a good vacuum, and go back the way it was intended to be.  Yes 134a will work for a while and it will be cool to, but....... See how long of a warranty the shop will actually give you and what the warranty on the parts is.  I have been down this road quite a few times by trial and error. I was an automotive a/c tech for a decade or so. I learned on this type of particular system, it will last longer and work as it was intended, going the correct route. The compressor has a head gasket, piston rings and a rod. It wasn't engineered for excessive high pressure and high rpm usage for any type of extended time.   I believe I have converted around 12-15 units throughout the years , but way back. I warranted just about every system and converted it back to r12.  And when the dryer goes ka put, so will the expansion valve and also start plugging up the whole system causing a flushing nightmare.   Yeah, you will have cool air for a while, but when it goes out, you will experience the song n dance theme.       You can get an r12 system to last close to 15 yrs or more, A 134a conversion the way you are say will last a very short time before you see signs of deterioration.  This is just my point of view from my experience, not intending you to stop what you are doing, there is more to it than pag oil, special color o ring gaskets and new hoses. Your system was built for 100,000 different types of people using the system. A conversion was made to go cheaper and go green with the environment.  It is a snowball affect, you know?  Do some searches and research before you commit.

[Aussie Challenger]

   If you do go down the R134 route fitting a larger condensor will help slightly to allow it to cool better as the R134 gas is no where near as efficient as the good R12. At least you can still get it in America, here in Australia it is banned out rite.