the thread says it all. 1988 560SEL a/c compressor keeps kicking off for no apparent reason.. from a stop and while under way.. Anty input on this problem would be great also.

May be a loose belt may be causing your problem...

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J.H.
'86 300E

look for loose or broken wires to compressor,and make sure a/c system has correct charge on it.
there is a temp. sensor on the engine that cuts out comp. when hot,i've seen these so bad they would cut out compressor just by touching it.
mf

There is a sensor that cuts out the compressor when the belt slips. It is very likely a loose or improperly tensioned belt. It also could be a failed belt tensioner.

Good luck,

the 560sel has indivdual belts for each diven component and is not equipped with a compressor speed sensor.
MF

I don't think your car has a speed sensor on the AC. Check to see how many wires you have on the compressor plug. You probably have only one which means you don't have a speed sensor and can eliminate slippage as the problem.
The best thing to do is take it to a tech and check for proper charge. Not enough or too much freon will cut out the clutch or maybe it's just one of the sensor acting up.

Vinamg

Thanks for the help so far guys....the compressor cutting off isn't so bad but it won't come back on without turning the a/c of then back on..Does that help?

I would suggest that there are problems with the climate control computer. I have seen several with microcracks on the printed circuit board that caused intermitantcies.

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Well, I'm showing my lack of knowledge of the big body cars. I'm surprised that there is no sensor.

If the problem is in the climate control unit, heating the solder joints might be worth a try. I know it is not uncommon to fix a 124 Climate Control. This will repair a cold solder joint(not totally uncommon) and can fix a broken circuit board trace.

Also, ensure that the system is fully charged. If the high side pressure is too low, it will cut out the compressor. Since this is happening on acceleration this is not likely.

Good luck,

do search on acc or a/c cut outs, lots of info.

Joel I get 4 matches which are nowhere close to my symptoms. Any other ideas

If it's not too much trouble would you post your V.I.N. number ?
The problem you stated is exactly what you would expect from an engine equipped with a serpentine belt and comp. speed sensor.
If your car is in fact a 560 it has niether.
Your V.I.N. # will tell .
MF

Mike is certainly right about V8s not having speed semsors in 126 body cars.

The way to the answer is to decide which controller is dropping out. If the temp sensor is the problem then the push button controller is going to be the one that shuts down. The PBC (pushbutton controller) is the one that decides "when", the compressor controller decides "if". The signal from the PBC is a ground signal that drops the voltage coming from the compressor controller and goes through the low pressure switch. This is the easy window. First verify that the proper signal is a ground by watching the signal at the circuit through the low pressure switch (some models use a power signal - only diesel 201 bodies i think but I always verify). Turn the A/C off and on and verify that the voltage is high with the A/C off and low when the compressor is on. Next get the condition to exist and see what is happening at the low pressure switch. If the circuit is still grounded then the PBC is doing its job, the temp sensor can't be the problem and the problem exists in the compressor controller under the hood.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve thanks for the direction. I will give it a shot after work. I read the pressures last night. reading 35/ 175 at idle...18-22/190-200 under acceleration. Does this help.

Hey Mike thanks for the input. The car is a 560 SEL. Have it almost 6 years this year. I know that is sounds like a velocity sensor problem but that's not it. Wish it had one...Wouldn't have blown the compressor a few years ago. Thanks again Mike.

Brian