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Old 04-16-2002, 08:44 PM
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Join Date: Mar 2002
Posts: 14
R12 to 134A

Evening folk's...I just replaced the expan. valve and drier (fun job!! NOT!!) on my 1990 type 126(420) and I'm ready to get it recharged. Everone wants to recharge it with 134a. Thats fine with me as long as it works. Do you need to flush out the system,even with the new drier? Are the oils compatible? Do you need to change the fan switch? I have a can of R12 and one guy said he could use that and top it off with "Freeze-12" but after reading the last post on that topic I'm a little leary...Any ideas?!? Thanks guy's!! Larry
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Old 04-16-2002, 09:21 PM
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Join Date: Apr 2001
Location: Baton Rouge
Posts: 485
Freeze 12 is a propane based freon unless you want a new system stay away from it. To convert your car from 12 to r134a you need to drain oil from compressor and replace with PAG oil or a compatible oil. We use BG flouresent oil cause it is compatible with 12 and r134a , also will help spot leaks in future.
After you drain compressor pull vacuum on system for no less than 25 minutes , add 5 ounces of oil in low side hose and add 15% less charge to system . Say it takes 2.4 lbs of r12 , well I would charge it with about 1.9-2.0 pounds of r134a. Sometimes you have to start off with least amount and add while watching pressures and a thermometer in the dash. The only cars I do not recommend retrofitting are cars with weak compressors ( needles fluctuating, nippendensos are bad about this) , vehicles equipped with a-6 or old york compressors. The r-4's come out perfect for some reason and a good nippendenso will cool well also. Dont expect a miracle at idle in traffic though. Best nippendenso job yet was 46 degrees at idle in 100 degree weather. Rare occation down here . Well hope I helped good luck.
euro 287
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck
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Old 04-16-2002, 09:22 PM
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Join Date: Jan 2002
Posts: 17,502
When I switched from r-12 to r-134a in my 1977 Buick I found that the belt had a hard time carrying the increased load from the higher pressures of the 134a. It would always slip and screech then I turned on the air and it sometimes took a mile or two before it stopped.
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Old 04-17-2002, 12:39 AM
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Join Date: Apr 1999
Posts: 2,632
I would install dual pusher fans in front of the condenser, and yes changeout the pressure switch for one compatible for R134a pressures.

I also replaced my viscous fan with a SPAL 16-inch and in stop-n-go 97-F desert heat (Las Vegas) the A/C was still cool.

All this in a black 1988 W124 wagon that was initially filled with R12.

:-) neil
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Old 04-17-2002, 02:55 PM
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Join Date: Mar 2002
Posts: 14
Thanks for the info guy's...I really appreciate it!
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