Re: [DML] AC R134a Retrofit Kit

["Harold McElraft" <hmcelraft@xxxxxxx>]

You will need to remove as much old mineral oil as you possibly can 
by flushing the system - preferably a component at a time and then 
replace the accumulator - and orifice tube while you are there. The 
proper measure of new oil is critical - there is a lot of hose in 
the D system which requires a little extra oil but about 10 oz is 
the max in a clean system including the 1 oz in the compressor - 
actually the stickers on some compressors call for 1 cubic inch of 
oil which equals .554112 oz - I use 1 oz. (according to Four 
Seasons - too little oil is the most common reason for failure of 
compressors for replacements and retrofits). If your system does not 
have a high side pressure switch you should probably install one. 
Many do not but 134 runs at higher pressures and possible damage can 
occur. The DeLorean cooling fans out front do a minimal job of air 
flow at slow speeds adding to the high-pressure risk. The charge 
should be about 90 percent of the recommended R12 charge of 2.2 or 
2.5lb depending on which manual/bulletin you believe (2.2lb) is my 
preference (I use R12).

The modern recommended way to check for a proper refrigerant charge 
in an ac system (R12 or R134) these days is measuring the 
temperature delta between the evaporator outlet pipe and the inlet 
pipe with full load on the system with all components appearing to 
be operate normally. With 80 degrees ambient air temp, doors open, 
engine at idle speed, fan on high, mode switch on max - check the 
temps. No easy task to get to piping however, but can be 
accomplished from inside the car at the bulk-head if you're flexible 
enough. Evaporator outlet temp more than 5 degrees above inlet temp 
equal low charge. Outlet temp 5 degrees below inlet temp indicates 
an over charge. The ideal temp delta is zero.

Harold McElraft - 3354




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