90 Mustang Air Condition R134 Conversion

Changed mine years ago, the only thing I replaced was the orifice hose, which was why I took it apart and the O-rings on the compressor. The orifice is crimped into a length of steel line, and the steel part in-between the hose has a foamy insulator. Obviously condensation collects in the foam and starts the steel tube to rust and pit. It developed a leak. I also changed the drier.

Whjen converting Ac systems was in it's infancy, the engineers were worried that older systems couldn't handle the change and had us change a lot of parts - as it turns out, not with any real necessity.

The system should be drawn into a deep vacuum and as much oil removed from the system as possible. The suction accumulator or receiver/drier should be removed to get what oil we can out of them (but that's me being nearly as anal as the engineers) - of course, we would replace the O-rings at this time. I would like to R&I the compressor and remove what oil I could at the same time.

Once we are this far, we can add the appropriate amounts of oil (memory thing coming.... about 3 ounces in the compressor... a couple of ounces in the receiver /drier or suction accumulator... an ounce or so in each of the condenser and evaporator and charge the system....

Here's the rub... many owners have had good luck simply doing a refrigerant drop.... This is more luck than design IMHO... If you are looking for years of reliable service without a compressor failure changing your budget, the more we do when changing over, the better our chances.

YMMV

If you want to avoid the incompatible oil issues and potential reduction in cooling capacity don't use R134 but get Freeze-12 instead. If your system didn't have any real problem but you just want to convert all you'll need to do is pull a vacuum for an hour or so and then put the Freeze-12 in. I just put the system in a 64 T-bird back in order and used Freeze-12 and it was putting out 45 degree air today in Phoenix.