I looked at the dieselgiant site's information on A/C repair, and dropped the cash for the DVD. (BTW-- it's probably worth the bucks, if you've never done "ANY" A/C repair!)

I was getting things together to get started, new drier, new expansion valve, refrigerant and 'oil..' I was going to draw it down today-- and get to work this afternoon.. My freeze-12 (drop in "Freon" replacement) arrived a couple days ago..

Here's my problem.. Uncapped the lines, to find one has been "retrofitted" to 134a.

My questions are:

1) can I just wrench that off?? It looks like it's just a screw on fitting.

2) the BG refrigerant oil is compatible with both 134 AND R-12 "freon" so I'm thinking that isn't an issue..

3) do I need to replace the receiver drier and expansion valve, and pretty much, go on with my life??

BTW-- my compressor clutch connected and ran for a few seconds without horrific noises.. I think I'm okay there...

I'd really PREFER to go back to the R12 (Freeze 12) setup. One, it's already paid for, two-- it's closer to what 'Ma Benz designed the system for.. 134 seems fine, for what it's designed for-- I've never been impressed with it for retrofits... I did a couple for others when Freon first became scarce, and before reasonable alternatives like Freeze-12 were available. Their systems didn't work 'as well' or blow 'as cold...' The compressors seemed to die about 2-3 years later.. We told ourselves they were old compressors-- but I now understand that 134 operates at higher pressures-- and that stresses the compressor more..

Anyway-- any help would be appreciated..

AJ

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Agnes (the Limo) '84 300SD
Pearl (the Taxi) '81 240D (preparing for the 'afterlife')
Bridgette (baby girl) '82 VW Pickup-- currently getting readied for her rebuilt (overbored) engine.
1 VW 1.6 NA diesel **not installed in vehicle**
Gidget (the bimbo) '87 VW Cabriolet-- the diesel engine it above is eventually going there!

and a BMW Motorcycle. (1998 R1200C)

Did I mention I'm of German Heritage??

Freeze-12 is just a mixture of ~80% R134a and ~20% R142b.

If the original R134a conversion just added POE oil to the system and left in the original mineral oil (to settle "harmlessly") and you now add more BG oil,....you have an issue. The 134a is miscible with the POE and the BG; the 142b is miscible with the mineral oil and the BG, so you have a LOT MORE oil circulating in there (3X conceivably) than you think. Possibly enough to pop the reed valves in an R4 compressor. "Slugging"

Since you don't know the previous conversion status (and oil composition or amount), flushing the evap, hoses and condensor would be on my "must do" list.

Freeze-12 cools with R134a, the 142b is to carry the original mineral oil so Johnsen's can infer that it's a "drop-in" replacement fot R-12. How this can cool better than straight R134a is beyond me.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)