R107 AC compressor questions

1971-1989: 280SL, 280SLC, 300SL, 350SL, 350SLC, 380SL, 380SLC, 420SL, 450SL, 450SLC, 450SLC 5.0, 500SL, 500SLC, 560SL
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Model you own: w107

R107 AC compressor questions

Post by Teije » Mon 28 Jul, 2014 11:50 am

Hello everyone,

I have a question regarding the ac compressor of my '72 350 SL:
The pulley spins freely when the clutch is not engaged. When the clutch engages however, the pulley comes to an immediate halt, like something is blocking it.
The clutch itself spins easily for about 3/4 turn then it "blocks". it almost feels like there is a bolt or a lock preventing it from making a full rotation (it feels a bit like the time when I put one too long wheel bolt in the rear wheels, the wheel spins fine until the bolt hits the handbrake assembly)

As this car does not have an electronically activated low-pressure cutoff valve, I am wondering:
Can this be a very primitive kind of mechanical low pressure cut-off? There is pressure on the system, but maybe not enough.
I would think that if the compressor was seized, it would not spin at all, but that's not the case.
Another question is: Does anyone have experience with removing the clutch assembly with the compressor still on the car..?
The compressor is an Unicla DA-290
Thanks for your input,
cheers Teije

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Re: R107 AC compressor questions

Post by AMG » Mon 28 Jul, 2014 11:13 pm

All the compressors i have fitted to my cars are all Sanden, so not much help to you there. Are you sure it is not aftermarket a/c? Is the car Au delivery?
1987 560SL 4sp. auto Signalrot "Stella"
1987 190E 2.3-16 5sp. man. Blauschwarz "Hermann"
1992 300CE-24 6sp. man. Perlblau / Iceblau "Gretel"
1992 Range Rover Classic 4sp auto Ardennes Green "Oswald"
2012 E63 AMG Speedshift MCT Diamantweiß "Klaus"
1986 560SEL Anthracitgrau "Schultz" - In Mercedes Heaven
1987 190E 2.6 4sp. auto Signalrot "Sabine" - which now resides/owns Andrew M's Garage
1972 350SLC Astralsilber "Lurch" - now in the loving care of Craig B
1989 2.5-16 Blauschwarz 4sp. auto (parted) formerly owned by Derek/Hasan.
2012 Renault Sport Megane RS265 Trophy 8:08 6 sp. man. Liquid Yellow "Jean Rédélé"

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Posts: 30
Joined: Tue 12 Nov, 2013 8:36 pm
Model you own: w107

Re: R107 AC compressor questions

Post by Teije » Tue 29 Jul, 2014 4:05 pm


thanks for your reply. The car is Au delivery so I think the AC was factory. I did some more research, I am now confident that the compressor is a York-type compressor but the brand is definitely Unicla. So it looks like the factory unit has been replaced at some point in its life with an imitation York compressor by Unicla.
Problem remains however, why doesn't it rotate..? I found a manual for York compressors online so to start I think I'll take the clutch assembly off...

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Greg in Oz
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Re: R107 AC compressor questions

Post by Greg in Oz » Tue 29 Jul, 2014 11:28 pm

My 500SLC has factory air as did my old 350SLC. I can't recall what compressor is fitted to the 500 but the old 350 had a Frigidaire (General Motors) compressor. I don't believe that is especially relevant in your situation as I believe your compressor may have had a serious failure. For it to stop suddenly at one point in its rotation and not be able to be turned a full revolution by hand sounds serious. I don't believe removing the clutch assembly will achieve anything as I suspect it will be something more serious within the compressor.
107023 - 350SLC: 1973, 3sp auto, icon gold, parchment MBtex (sold July 2012 after 29 years ownership)
107026 - 500SLC: 1981, 4sp auto, thistle green, green velour
124090 - 300TE: 1990, 4sp auto, arctic white, cream-beige MBtex
124090 - 300TE: 1992, 4sp auto, malachite (spruce green), black MBtex
201024 - 190E-2.0: 1985, 5sp manual, black, black MBtex
201028 - 190E-2.3 Sportline: 1990, 5sp manual, arctic white, blue leather
201028 - 190E-2.3: 1992, 4sp auto, blueblack, grey MBtex
201028 - 190E-2.3 Sportline: 1990, 4sp auto, signal red, black cloth (parts car)
201034 - 190E-2.3-16 Cosworth: 1985, 5sp manual, blueblack, black leather
YG2S8 - Mini Clubman GT: 1972, 4sp manual, blue, parchment vinyl (my first car which I still own)

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