Well it sounds like your research is getting you somewhere of which I'm not familiar so I guess I will bow out on it. I will add though, that the aux fan is actuated to pull down high side pressure which is obviously not a problem in your apparantly undercharged system. It is also actuated by high engine temp. I would continue working through the other problem before worrying about the fans. In all likelihood there's nothing wrong with the fan controls from what you've said.

Good luck

I am getting some more results now that I have gauges

My fans seem to come on sometimes at 200,sometimes at 250 and some times they don't come on even at 250

On the other hand the cutout seems to occur independent of the high side pressure. It happened once at 225 and once at 200.

It may be however that while I am driving and cannot read gauges the pressure is getting high enough to cut out compressor becuse my fans are not coming on soon enough.

What pressure should cause the fans to come on?

What pressure causes the compressor to cut out?

Thanks

I have been away from the forum for several days. I had to go out on assignment Thursday and Friday and then go with my wife to her Marathon, 40th High School Reunion. It included events Friday night, Saturday and Saturday night. It turned out to be a fat peoples convention. My wife who is slightly overweight looked as skinny as Twiggy by comparison.

Anyway I'm not making much out of your evaluation and it's REALLY difficult to troubleshoot something like this from long distance.

I think that the fans are turned on by either high engine temp OR excessive high side pressure. I would expect the excessive high side pressure level to be somewhere around 250.

If I am understanding the cutout portion correctly, it really sounds as if you have a worn compressor allowing for false rotational sensor activation. IF that is a correct assessment, you can either find out how to cheat the klima on your later model 124 or replace the compressor. I really hate to see you replace the compressor on my say so, since I've never seen the car.

Do you have a Factory Service Manual?

wrooper, If I recall correctly, your vintage 124 uses a pressure switch to activate the aux fan low speed at 20 bar pressure, and to turn off at 15 bar. Doing the math in my head, 20 bar is somewhere north of 290 psi. That is, if your pressure switch has a red base. If green, the corresponding specs are 16 bar/12 bar.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

I reread the manual for this car and believe it rules out the speed sensor. My careful reading indicates the speed sensor function is only active at startup.

The only other cutout function I have not addressed beyond cleaning is the clutch gap or coil faulty,however I would be surprised if the magnet,once it has engaged]would drop it's connection. ie once the clutch is in contact even a weak magnet should keep it in contact.

Anyone have experience that contradicts either of these cases?

Thanks in advance