R-12 to R-134

[Clint F.]

1. receiver/dryer (don't remove the caps until ready to assemble and vacuum 
the system)
2. all o-rings at connections you have apart replaced with green nitrile 
rings
3. flush as much oil out as you can, it won't dissolve in the 134, and pool 
up in your system.
4. 30in" of vacuum for an hour(the longer you can pull the vac., the better 
it seems to go)
5. schrader valves
6. new 134 fittings
7. PAG or ester oil for the 134
8. close to 80% charge of 134 of what your car calls for using r12
9. possibly, new pressure switches

Sure, you can buy the fittings and a can of 134, or some "universal" 
refrigerant at your local "parts4cheap" store and shoot it in, but save your 
X-mas money for a new compressor next year.

134 isn't as efficient as r12, especially in a car made for r12, but you 
probably won't know the difference.  The sight glass is useless for charging 
with 134, the bubbles will never stop. Also, 134 runs at higher 
temperatures/pressures, so if you have a weak link in your system(ie 
compressor, hoses) you will know about it.

This may seem excessive, but many of the generic additives contain propane. 
You want that to be the first thing to bust in a crash? Changing the oil is 
important to allow the correct amount of refrigerant in, and to properly 
lube the compressor. This is a general guide for most retrofits.  134 will 
work fine in a retrofit if done right, your hard parts will last just as 
long, and it will keep you nice and cool in the middle of July.
Good luck,
Clint

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