ABS light found diff plug off

[Rich]

Hi all,

So since I bought my car I was told the diff has been blanked off and to be honest never touched it or even looked into it.

But today I thought why and noticed whilst changing the diff bush I noticed the electrical plug on the rear diff was unplugged so have plugged it back in but now have a constant ABS light, and looking back through MOT history I see is had a failure for ABS light to be on. So thinking they have done this to mask a potential issue.

Does anybody know what causes this?

Thanks in advance

[Bowie69]

Without looking at the diagram , I'm suggest either there is a wiring or switch fault which is sticking the difflock in (ABS is disabled when difflock is in, for obvious reasons, once you think about it), or the switch in the diff which turns the light on is faulty.

[Rich]

Yes the green light is on, indicating it is locked but it doesn’t feel like it’s locked, nothing happens when I press the diff button but i can here clicking inside the car when pressed.

[steve briance]

It the actuator connected? Mechanically to the diff and also the vacuum lines? I've never had any bother with mine touch wood but I wonder if the plug is removed to mask a problem with the actuator itself? I'd imagine you would know of the diff was actually locked though as the rear tyres would scrub a lot.

[Rich]

Actuator is connected although just noticed the check valve Under seat is blanked does anyone have a picture of how it should be under the seat

thanks!

[Mr G]

This should help - courtesy of UrS4boy
https://www.s2forum.com/forum/techni...s4-and-95-urs6

[Rich]

MR G! Awesome thanks!

so after I connected the vacuum pipes back up, I removed the sensor in the diff to confirm this was working which it was, then I moved the actuator back to disengage the diff. Then I pressed the diff button but when pressing diff button again the actuator does not return by itself I have to formce it back manually.

any suggestions?

thanks

[steve briance]

Are the pipes on the right way round? Tick the simple things off first how about unbolting the actuator from its bracket and see if it moves as it should with no load, that way you can see if it moves and if so how much force it can exert. If it barely moves then it may be perforated diaphragm?

Pic is my actuator to remind me which way round the pipes go when I put it back

[M2ki]

MR G! Awesome thanks!

so after I connected the vacuum pipes back up, I removed the sensor in the diff to confirm this was working which it was, then I moved the actuator back to disengage the diff. Then I pressed the diff button but when pressing diff button again the actuator does not return by itself I have to formce it back manually.

any suggestions?

thanks

Probably crack in the actuator. You can blow into the yellow striped tube to confirm.
If thats the case, buy a mercdez door lock actuator and modify it or buy a new one from tradition.

[Rich]

Thank you all I will investigate further on Monday