R134

[mrfirebird]

has anyone changed over there R12 to 134 freon ? i saw a kit at advanced auto and mine needs recharged , this would a good time to change over , if no one has had problems.

[candywrapper]

Mrfirebird;
I have a 91 pontiac Grand Prix that i just switched over from R-12 to R134. this is what i was told by Advance Auto. first you have to make sure that no R-12 is in the system. you do this by a AC vacuum pump,luckily my boss had one for me to use.Anyway This is very important because R12 and R134 dont like each other,it will goo up your system .Allso ,when you do this ,you can tell iff you have a leak some where before you put in R134.It should only take 5 or 10 minutes for the vacuuming. You want aleast 10 to 15 lbs of vacuum .once that is done you can put in the R134.Auto Zone usually can rent you a vacuum thing.Advance dont rent stuff. you can get the retro kit usually at one or the other,advance or auto zone or at Walmarts for around $35 . the retro kit comes with everything to put in the R134.I dont think you want to use R12 anyway, its like $65 per can,and you need a Mec licence or something to even get the R12..the usual ac takes around 3 or 4 cans of freon.This only took me less an hour to do. when you get the retro kit , READ the instructions first,otherwise you could mess things up.Im no mechanic. this was very easy to do
Don

[Mikado14]

Well, it doesn't really matter on the make, since you didn't post it I will assume we are talking about a '94 or older Blazer. First, you will need to recover the R12 from the system unless it is all vented from a leak, which I assume that is the case. There are several ways you can approach this. At work, I will change out the following: accumulator and orifice tube. My advice is to flush the evap and the condensor and when you do the condensor, try to capture the flush and inspect for any contaminants such as metal from the compressor. If there is any metal or if you have had a noisey compressor or there is evidence of oil leakage around the clutch perhaps you might want to consider replacing the compressor. You will need to drain the oil from the compressor if reusing it and replace the captured amount with ester oil. You will need to find out the amounts of oil to put into the new accumulator, into the flushed evap and the condensor. Use new o-rings when reassembling and remember to coat the new o-rings with ester oil. Ester oil is compatible with both R12 and R134. DO NOT use PAG oil (compatable with R134 only) or mineral oil (R12 systems only). There is bound to be residual oil somewhere in the system so use the ester oil. After you have reassembled the system, install your new adapters for the R134 and the system will need to be vacuumed down. Pumping down should be done for a minimum of 30 minutes. After you are confident of your pump down, charge the system with approximately 70% of the original R12 (actual percentages are approximate for I usually adjust the amount via a chart as to ambient temp, condensor temp and vent temp as well as humidity all to keep what is called the slide within design parameters). Now the tricky part. You can either replace the low pressure switch on the accumulator with one adjusted for the R134 or you can adjust the old one. Adjusting is done by unplugging the wires and at the bottom where the wires plugged in there will be a rubber plug. Remove this and you will see a small screw head. Oh heck, just replace it. The procedure is tedious and my fingers are getting tired from typing, do this prior to pump down. If you do decide to adjust it, 26 lbs on the low side should be good. I have adjusted these down to 21 lbs to get a little more out with success. Hope I covered most of it, if not, I will post again. Good Luck!!