If anyone is contemplating a switch from R-12 to R-134
in a 1961 or later Mopar, I've had very good results
doing the following:
1. Change oil in compressor. I had a new one with the
correct oil already in it, so this process was not
necessary.
2. Have system flushed of old oil and contaminents.
3. Remove EPR valve from back of compressor. This
valve works a little too well with R-134 when the
temps get high, restricting cooling ability.
4. Since there is no longer an EPR valve to prevent
evaporator icing, a thermostatic switch should be
installed that cuts off the compressor when things get
too cold. Then cuts it back on when the threat of
icing passes. Yes, R-134 will cool so well that icing
is an issue.
5. R-134 typically works at pressures above R-12, so
it would be a good idea to install a safety cut-off
switch on the high side.
6. Optional: An auxiliary fan in front of the
radiator will help to lower condensor pressure and
temp for better performance in stop-and-go traffic.
The fan can be manually operated, or be wired to
operate when compressor is running.
Note: With the externally-mounted by-pass (EPR) valve
in 1960 and earlier compressors, I have found that
they do not work particulary well with R-134.
Apparently these extarnal valves don't allow correct
pressures to be maintained with R-134. And since
these valves can't be easily removed, a switch to a
later RV2 compressor would be necessary to get good
results from R-134. (Bolts right on to existing
brackets, but later hose connections would also be
needed.) Or stick with R-12.
Keep cool,
Chris H.
60 NY T&C (R-12)
66 LeBaron (R-134)
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