I'm trying to figure out a 1986 560SL that has 2 A/C problems. #1. The climate control comes and goes after hitting bumps. When it works there is power at both sides of the fuse (#6). When it quits there is 0 volts at the fuse. So, whatever powers up the fuse has a problem. A bad connection or relay or whatever. Note: The fuse is good. Unfortunately I don't have a manual for this car, just my SEL. #2. (Probably related to #1) When I say the climate control is working, I mean air is blowing out the defrost and side vents only. I understand this is a default mode and means the climate control has a problem. Only rarely does the compressor engage and when it does there are bubbles in the sight glass. I tried adding freon but I'm unable to get the compressor to engage even though I jump the low pressure switch. Reading other threads I'd guess a bad control panel, but I'd like some input from someone with more MB experience than myself. Thanks.

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Tim Mabry
87 560 SEL
85 Chrysler Laser
72 IH
59 Rambler Rebel
57 DeSoto Sportsman
55 New Yorker
49 Dodge Turdmobile
47 DeSoto Suburban
40 Packard
39 Packard

This could be a number of different things. The Klima relay, compressor speed sensor, slipping belt, bad high pressure switch, the ACC itself. if the system pressure is too high or the high pressure switch is malfunctioning, there is nothing that the low pressure switch will do to get the compressor turning. If the compressor is not engaging long enough to pressurize the system, the bubbles will persist. Troubleshooting should start with the simple stuff, belt slippage, high pressure switch, proper system charge and a good read on the pressures when and if you can get the compressor to stay engaged long enough to get a reading. A static pressure read on the low side might be useful (maybe). But, I think you might have to sub or replace the ACC to eliminate that component because it interacts with all of the other components.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

I have a similar problem with my 560SL - 1987. The AC only comes out the defroster and side vents. You mentioned that this is some type of default mode. The compressor seems to take a little long to turn on also. Eventually, pushing the control buttons randomly gets that part working. I also do not have the maintenance CD. Any guidance would be appreciated. This is more of an annoyance than anything else! Thanks a lot.