By all means, replace the filter/dryer. The new compressor warranty probably
requires flushing the system, too.
I bought an a/c flush kit from JC Whitney-it worked just fine but it's quite
messy...don't even think about flushing the system indoors.
Once the compressor and filter/dryer are removed, it's easy to flush the
evaporator and condenser from the compressor fittings.
My first attempt left some flush in the system (I didn't blow enough compressed
air through the system to remove all the flush due to ignorance and being
overwhelmed by the mess) and I couldn't get any suction from the compressor. I
removed the hoses and filter dryer and repeated the process with compressed air
until only dry air discharged from the system.
After reassembly, and a lengthy run with the vacuum pump, the system works
great. I should mention that this was a lesser Mopar...a K-car, in fact, but
the procedure is the same.
A few final thoughts: your new compressor's crankcase should be full of oil.
Make sure the quantity of oil in the compressor is equal to the total oil
required by the system since you will have removed all residual oil. Consider
replacing the two schrader valves and the expansion valve. R-12 is expensive
and your system probably requires about four pounds...it's a gamble putting
that much R-12 in an antique system. It might be a good idea to put a minimal
charge on the system, close the gauges, and check for leaks with a
"sniffer"...or at least let the system set overnight to see if it holds
pressure.
Phil Brust
73 & 82 Imperial
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