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A6 Compressor oil fill

Started by daantjie, 03 August 2022, 08:31 AM


Hi guys

Stumped a bit over here...I bought a new Alma compressor for the 6.9 and right now balls deep into the swap.  Indeed this is a "fun" jobby...

The supplier states 10 ounces (300 ml for us mere metric mortals  8) ) was shipped inside, but I drained it out and only found about half that at most.  It's very difficult to drain the bloody thing as it weighs a TON.

I am putting mineral oil back in for R12 but now I'm worried as to how much to put back in.  I really don't want the bloody thing to lunch itself after all this back breaking work.



1977 450 SEL 6.9 - Astralsilber



The service manual in the technical section  83-520 (under "service manual library" and climate control), has filling capacities for three different compressor types.  Check it out it should get you close.

1979 Mercedes 6.9 #5206 - restored
1979 Mercedes 6.9 #6424 - ongoing restoration
1976 Mercedes 6.9 #484 - restoration?


Thanks looks like the A6 GM/Delco/Harrison unit calls for 300ml.
1977 450 SEL 6.9 - Astralsilber


Well, I charged her up and got 12C at the vent so I'm putting this one in the "W" column ;D for now at least hehe...
I did rotate the clutch unit about 20 times once installed and before running the compressor as everybody online says you need to do this to push excess oil out of the discharge port to prevent hydrolock.  Might be bullshit but I was not going to risk it.
1977 450 SEL 6.9 - Astralsilber

s class

Bit late to help, but I've fitted a fair number of those apco units.  I usually drain the oil, measure with a syringe and put it back in.  It's typical to only get about 150ml out, if you leave it draining overnight you might get about 220ml out, we'll that's the best I've ever managed.  The rest remains trapped in the various internal chambers.  So yes, despite my concerns, I believe that every unit I've bought did in fact have the claimed 300ml in. 

It's worth pointing out that PAG oil for R134a and mineral oil for R12 are immiscible and having a combination of the two results in a jelly like coagulation and shortened compressor lifespan. 

When we do compressor replacement, we usually do a 'full house' with all new lines, New receiver drier and expansion valve, and chemically flush the evaporator and condenser to eliminate any traces of mineral oil when going over to PAG/R134a

[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL