Auto R12 to R134a

[jeffhynes]

Hey guys,

I'm new to the forums and currently studying mechanical engineering, so I hope I don't mislead anyone by my "mechanical" title.

Anyways, I'm looking to put air conditioning in my 1968 mercury montego and have an orginal under dash unit that was designed for R12 (Freon).

Specifically, I was wondering if there are any generally known guidelines for getting the most performance out of an ac system given a fixed evaporator coil (also keeping in mind it was designed for the more efficient R12 gas). I'm looking for something which would point me to finding an appropriately sized condenser and getting the most out of a retrofitted R12 system.

Also, is it possible to increase the performance over freon by compensating with a larger condenser, more efficient compressor(Sanden), etc.?

Thanks,
Jeff Hynes

 

[RossABQ]

I had several 60's Mustangs with the under-dash unit, and can attest that they didn't exactly make any nipples hard, even when new. There are several aftermarket outfits that make brand new retrofit R-134a systems for your car, that mount similarly. That's the high-buck approach.

If you're budget limited, change all the hoses to newer stuff (just due to age, the permeability issue isn't as big a thing as was once thought). Change the oil in the compressor to ester. See if there is an expansion valve made as a direct replacement for 134a operation, I think there are some. A later model condenser wouldn't hurt, just go to a boneyard with your condenser's dimensions and a sketch of how it attaches to the radiator panel. You can have any kind of connections you want brazed on by a radiator shop. Ford condensers of that era weren't particularly large, especially the add-on's. I know there are Mustang/Cougar fanatic websites, you should check in with them to see what others have done.

A great resource website and forum is:

http://www.aircondition.com/