Auto Air Conditioning & Heater Repair: r12, gm systems, galvanic corrosion

Question
I have a 1992 cadillac deville. I was wondering how hard would it be to replace the r12 seals in it. I have a brand new bottle of r12.

Answer
Sean,


 A seal kit is very inexpensive for a 1992 Deville but where you might have problems is actually getting the lines apart to replace them without damaging the lines and or fittings.
 That system is a cycling clutch orifice tube system that the climate control module monitors cycling to disable system if refrigerant is low.  Remember that after repairs you may have to reset by disconnecting the battery before the CCC allows compressor actuation.
 The difficulty I have replacing those seals starts in the climate I am in.  In northern parts of the country they use copious amounts of road salt and we have a very moist climate.  The fittings corrode, lines corrode and you get electrolysis and galvanic corrosion between the steel fittings and the aluminum lines.  The moment you turn the fitting it twists the frail line and will make them become porous and leak.  You may end up with more leaks after a reseal because of inadvertent line damage.
 Choose a line that is very accessible such as the top condenser one or orifice tube line into evaporator.  If you can break the line free with ease and turn it out by hand you might be ok.  If the line won't easily break free or turn out of the male fitting easily stop there.
 R134 works well in these systems and I usually will consider performing one evac, recharge and charge with 80 percent mass of 134A.  
 The unfortunate thing about the 1992's is you may have to fool the CCC into interpreting the new pressures correctly.  In some cases the low cycling switch may cycle too much and cause the CCC to disable the system as it thinks it is low on refrigerant.  You can accomplish this by installing an adjustable low pressure switch or install a variable orifice tube.  If you get to this step I can help you further.
 Hope this was helpful and don't spend alot of money on older GM systems.  They have a limited life due to deterioration of components.  If you are in Florida or Arizona etc it may be a candidate for a well done retrofit.  R12 is a chlorofluorocarbon and is restricted and damaging to our ozone layer.  R134 is a hydrofluorocarbon and also damages our environment as it adds to our global warming.  Some blends are ok but can be dangerous as they are flammable.

Wayne