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Old 03-04-2013, 11:00 PM
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ac conversion

I have an 84 chevy blazer that has the old r12 setup. The system has been inop for a number of years. I am going too go ahead and convert to r134. My Plan of attack is as follows. I am going to replace the acc/dryer with a new unit, fill system with 8 oz pag oil, vaccuum system for a couple hours after leak check and then service with r134 (80 % of r12 capacity). I have read about the inefficiency of r134. I dont need to hang meat in there. I just want a system that is operational. Anybody have any comments or suggestions on this project.........Steve

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Old 03-05-2013, 10:20 AM
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R-12 to 134 refrig.

I have been told the compressors, lines & seals will not work with 134
R-12 Freon Bottle W/24# + Guages + Adaptor Fitting - THE H.A.M.B.
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Old 03-05-2013, 04:34 PM
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Dont use PAG and dont pour in 8 ounces either.
Change the reciever/drier as planned. Get the new one with the X 7 dessicant ...compatible with r134a
Very important to change the orifice tube to a new one.
Unless you want to flush the entire system you should run a Synthetic PAG oil so it will jive with the mineral oil used in the R 12 system.
Cool blue makes a good oil. A Non synthetic PAG wont do well with an old R 12 system unless you flush completely.
If you choose to change the drier and orifice tube only, then pour 3 ounces in the drier when you install it. If you flush the system well, then add 2 to the compressor, 3 in the drier and put 1-2 in the condenser.
Flushing pushes out the old oil from the system. A bigger GM system with an R 4 compressor and an orifice tube only holds 6-7 ouces of oil total.
Dumping in an additional 8 ounces of oil, takes away room for freon, and raises head pressure, causing poor cooling.
Be sure to tighten up any area between the radiator and the AC condenser so no air gets in from the sides. You want the engine fan to positively pull air as much as possible. Air getting pulled in the sides between the Radiator and the condenser needs to be blocked to insure good airflow across the condenser, or cooling will also be poor.
Use 85% of original charge amount as new amount of R 134a.
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Old 03-05-2013, 04:55 PM
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In general I agree with LATECH's recommendations, but I don't really know how much oil the system will need.

If you switch to PAG you need to have the system really cleaned out of the old freon and oil, which is not easy to do unless you replace the compressor. You need an oil that can work with the old oil that you can't get out with a simple flush.

I used a Ford blue orifice instead of the GM white orifice that you probably have already. The orifice is cheap (about $2-3), so its not a big expense.

I also had better luck with a charge of R134 that was about 75% of the R12 charge.

New barrier hoses would be a good idea, but the old ones should work okay. You definitely need the new green seals, but the entire set only costs a few dollars.

Bruce
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Old 03-05-2013, 05:03 PM
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The ford blue Orifice tube is Good. it is a .072 inch as the GM white one. Problem is , unless you get a real saavy parts guy, you may end up with the old white orifice GM made that was .057 IIRC.(for R12)
Probably should grab the blue one as Bruce suggested to keep any guess work to a minimum.
Cool Blue SYNTHETIC PAG will mix with any oil, straight PAG will not.
I doubt the s 10 system holds more than 8 ounces of oil total. That spec should be easy to find.
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Old 03-05-2013, 05:12 PM
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You might want to think about replacing the front seal also. If the system has been empty that seal has probably dried out. At any rate hand rotate the compressor before running the system.

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Old 03-05-2013, 09:27 PM
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I am pretty sure that system was drained. I got it done today and completely forgot the orifice tube. She was blowing good cold air. If I need to I can change the orfice tube later. I have the guages and such. Ill let you guys know how it works out
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