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Old 08-19-2003, 06:02 PM
Registered User
Join Date: Dec 2000
Location: Fairfax County, Virginia
Posts: 856
Working on R134 System - How to Update R-12 Gauges and Hoses

Am getting ready to service an R-134 system. I have previously worked on R-12 systems and still have gauges and hoses ... my understanding is the R134 has different size fittings and hence the hoses must have these, too.

I saw converter fittings that allow the use of R-12 hoses and gauges ... is this an OK solution for occasional use? They were about $13 apiece (low and high) ... how about the cans of R134 ... they look like they require a different connector ..

Any advice of help would be appreciated!
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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Old 08-19-2003, 06:19 PM
dmorrison's Avatar
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Join Date: Dec 2002
Location: Colleyville, Texas
Posts: 2,694
It is not recommended that you use R-12 guages on a R134 system. You will contaminate the guage set, specifically the hoses. Then the R-12 and R134 will be mixed and contaminated in both systems.

1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car
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Old 08-20-2003, 07:34 AM
The Safety Geek
Join Date: Jun 2001
Location: Sudbury, Massachusetts
Posts: 252
I second the opinion above. You really ought to purchase a 134 manifold gauge set. The cross contamination will give you fits later on down the road. My $0.02
1995 E320 40K
1999 Tahoe 90K
2002 JX8 Sport 43K
2005 Volvo s40 65K
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Old 08-20-2003, 08:15 AM
Posts: n/a
You absolutely should get a new manifold, hose and adapter set for your 134 system.

There are indeed adapters and such available to switch back and forth, but the cross contamination risk is too great. When I bought my 134 set in the early nineties I had to pay big bucks for it. Now, however, a good set can be had for under $100.

Don't be penny wise and pound foolish, buy a 134 set. You will make use of it for the rest of your life.

Good luck,
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Old 08-20-2003, 04:16 PM
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Join Date: May 2002
Location: Mass
Posts: 1,127
The r-134a sets have sealed hoses that hold gas even after they have been disconnected. Most r-12 sets did not.

For this reason, cross contamination of gases in not likely using an r-12 set on r-134a, though there may be residual ester oil kicking around.

r-134a systems are more sensitive to moisture, so the open hoses are not the best. Really need to pre-purge the air out of them, but the EPA frowns on this (more than a little).

Getting a dedicated set is the best choice. They can cost as little as $75. Good investment, given the cost of A/C repairs.
1986 300E 5-Speed 240k mi.
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