E34 1991 535i ABS Warning Light

[yorkermiles]

Should the ABS warning light come on temporarily on the dashboard whilst the car is about to be started? and if it, is are there any immediate checks to perform to find the fault as I am pretty sure this is an MOT failure in the UK

[yorkermiles]

Anyone?

[whiskychaser]

It comes on when you switch the ignition on and goes out when you start the engine. If it DOESNT do that it will probably fail the MOT.

[yorkermiles]

I fear you are right,whilst reading through previous MOT's it has failed on this a few times and unfortunately the reason why is quite a mystery.Looks like there is one sensor to a wheel so I guess I had better start there and see if a simple clean up will do as the car has sat for a couple of years but any advice would greatly.

[whiskychaser]

If you think its a wheel sensor, use a DMM and check resistances. An odd one will stick out a mile compared to the others

[yorkermiles]

I have removed the instrument panel and tested the failing ABS warning light by inserting a known working bulb and yet it still fails to operate,in fact the brake wear indicator next to it fails too.
At the end of the day by my reckoning is that the bulb should work when the ignition is turned on and I would love to hear from anyone who has had similar problems as I am now thinking it is down to a faulty connection between the bulbs and the dashboard instrument board terminal/connectors.

I had a look at the board in the instrument cluster and where the ABS and brake wear bulbs connect to the circuit board of this speedo dashboad I could clearly see that there was an issue with the connections and it looked like the terminals on the board were damaged and sort of detached and ripped etc.
After a little TLC with a soldering iron I did get the ABS light to work when the ignition is turned on but the one next door which is the brake wear I think is still failing.
Its strange really because there is continuity at the bulb terminal and also on the circuit leading up to the terminal itself, so I am perplexed but at least I got the ABS on,thats an MOT failure in the UK.

I think the ABS and brake wear light might have been on for an extended period of time and damaged the terminals that way.I say this as after fixing the ABS light now it appears to want to stay on...ah this is fun.

[yorkermiles]

No the ABS light is fine now, thats one up on the MOT mechanic