Friend drives a 1990 300SL-24. The ABS light comes on with the ignition, but doesn't go out - it stays on all the time, and we're not able to find out why.. ABS is of course non-op.

Wheel sensor resistance OK, both front and rear. Haven't tried the signals from the sensors on a scope, but a bad or weak signal anyway shouldn't trigger the light directly after startup before the car has even moved - then it would go out and come back on when getting faulty readings.

Checked out the troubleshooting procedures in the factory shop manual, but it refers to some weird, old ABS tester that we of course don't have.

Any ideas on where to look next? Need to find out what's causing this, as the car won't pass inspection with a lit ABS light and it's overdue.. (and no, pulling the bulb temporarily won't make it pass - they check that it comes on and goes out)

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'95 E36T AMG (124.092)
'98 E200T (210.235)
'00 E430 4Matic (210.283)

Ok, so an ABS isn't really all that urgent a matter to fail an inspection. If you need to get the car to inspection ASAP to avoid late penalties then just temporarily daisy-chain another socket and move abs aside. The light will come on with ignition and then turn off. I actually did this with my CEL because I removed my smog pump. So I added another socket to windshield washer fluid light connection and disabled the CEL. See picture.

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1990 190E 3.0L

Problem solved! It turned out that this car, like most other older MB, did have an OVP relay. Replaced the fuse, no more ABS light, plus engine runs much smoother. Almost embarrassing.

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'95 E36T AMG (124.092)
'98 E200T (210.235)
'00 E430 4Matic (210.283)