Quote:
Originally Posted by Lurayfarmer
I've done this switch on several vehicles. The key steps are changing the charging fittings, changing the oil, thorough evacuation, and recharge. It is a good idea to change the receiver dryer which is a cheap part. A reputable shop can do this work for a very modest price. Forget anyone who wants to mess with the compressor, valves, hoses, seals, etc. That's just a way for a shop to take money out of your pocket.
As to cooling performance, I've checked vent output temperature with an AC thermometer. It's very close if not identical.
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Temps between R12 and R134a will be close until you get to about 95 degrees outside air temp...above 95 degrees, you will probably start to see increasing difference between the two refrigerants. This is due to the condenser not being large enough to shed the latent heat from the R134a. Now, with that said, my experience is mostly based on BMW a/c systems. It could be that GM oversized the condensers to begin with and thus this is less of an issue on our trucks. But, I doubt it.
As for the receiver/drier, most think if you open the system you MUST change the receiver/drier. I don't adhere to that camp. If you open the system, you can reuse the receiver/drier because when you evacuate the system, you boil the moisture out of the receiver/drier. That is why you leave the vacuum pump running for at least 30 minutes. Longer in cooler weather. But, if you change oil/refrigerant types, I say you MUST change the receiver/drier. But, changing the receiver/drier is never a bad idea, especially if they are old.