Intermittent ABS light

[HumbleJim]

Hi I've a problem with the ABS light coming on. Reversing off the drive on full lock triggers it. Turn the engine off and on a again it will often be okay for the rest of the journey.

I suspect a speed sensor or faulty wiring. A while ago I took the front sensors off gave them a wipe and all ok of 4-500 miles but now it's back.

The car is a 94 SL merc, I had a mobile MB specialist try to interrogate the faut codes, but this model is too early for proper electroinc diagnostics.

So I'll clean all the sensors (is WD40 okay for this or would brake cleaner be better) and inspect the wiring & connectors. Anything else simple I can do before I turn it over to a specialist?

I have a multimeter but because the fault is intermittent I'm not sure how far I'll be able to get. The last time cleaned the front sensors I had a "waggle" of the wires but couldn't get the fault to trigger.

I don't really want to play "Russian Roullette" replacing the sensors.

Thanking you all for your help ideas.

[stevieturbo]

A multimeter really wont be much use.

You'd need a scope to test each sensor in turn, or better together. But even then being intermittent, it isnt going to be an easy or quick task.

The fact it takes some time to happen would point more towards a trigger wheel problem than a sensor or wiring.

Inspect all trigger wheels to make sure they are in good order, perfectly round, no damage etc etc
And no wheel bearings are knackered

[HumbleJim]

Thanks, I'll take a look. Should I clean the tigger wheel?

[stevieturbo]

HumbleJim said:

Thanks, I'll take a look. Should I clean the tigger wheel?

That depends what the trigger wheel looks like and how you might intend to clean it !

[HumbleJim]

stevieturbo said:

HumbleJim said:

Thanks, I'll take a look. Should I clean the tigger wheel?

That depends what the trigger wheel looks like and how you might intend to clean it !

Old tooth brush.

[HumbleJim]

Tracked it down to passenger side front. Waggling the wire from the sensor set the lights off. Took apart at the connector re-assembled with some switch cleaner, reseated one of the loose clips and all seems good for now. Fingers crossed.

[PositronicRay]

Finally sorted this after living with it on and off for a yr (it could go for months without triggering)

Turned out to be the cable, quad core. When I stripped it back just one wire of the four was bad, crumbled and turned to dust. The other 3 were bright good conductors.

(name changed from HJ to PR)