1991 300E, 140K with original R12 A/C.

Once in a while I will find some shade and sit in my car eating lunch while listening to the radio. Obviously with the Texas heat I do this with the A/C running.

Today, I was doing the same - idling with A/C on auto and recirculate. I also had the headlights on. Anyway, at some point the ABS light came on and simultaneously the A/C blower slowed as if the battery was really weak. Actually, it seemed as if the A/C was going to shut off altogether, although the engine idle itself was smooth and normal. This seemed to coincide with the auxiliary condensor fan coming on (coolant temp was normal). I let this continue for about 5 seconds, then killed the A/C. Immediately the ABS light went out. About 30 seconds later I tried the A/C again, and within 5 seconds the ABS light came on and the blower slowed again, so I turned off the A/C.

I put the car in gear and started driving around, and turned the A/C on again. I ended up driving about 20 minutes with no problem whatsoever. This seems to have occurred only while idling with a heavy load on the alternator (a/c, radio, headlights, aux condensor fan).

I have done a search and everyone seems to think OVP is at fault every time the ABS light comes on. Is this my problem? It seems more like my battery or alternator output was weak since the problem went away while driving. Also, while the problem was occurring, the car idled smoothly and did not stumble.

Any thoughts? Should I plan on cleaning or replacing the OVP soon?

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