350SDL problem w/ABS,tach,A/C

I have a '91 350SDL. Occaisionally the ABS light comes on and I feel a load put on the engine. I assume it's the ABS pump that is the load. The weird thing is that the tach quits and also if the A/C is on, the A/C clutch kicks out. When this happens it usually happens for quite a long time -minutes rather than seconds although sometimes it is only a second or two.
The threads say to check the sensor, the harness connections to the ABS unit and the relay. The only thing I can find is the ABS unit with the electric motor and the brake lines going in and out. Is there another ABS unit? Also where is the sensor? (I used to have an '82 240D and had the Haynes manual. Is there a manual for this car?) Or a CD?

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Stan Rodbell
91 350SDl
83 240D

[mbdoc]

Sounds like the over-voltage relay is taking a nap every once in a while. It is the power supply for the computers that operate these items.

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MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V

Thanks for the reply. Is the over voltage relay a job for a do it yourselfer? Where is the relay?

quote:

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Originally posted by M.B.DOC:
Sounds like the over-voltage relay is taking a nap every once in a while. It is the power supply for the computers that operate these items.

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Stan Rodbell
91 350SDl
83 240D