ABS

[gumin]

Got my car back from the factory 2 weeks ago and among things they had replaced a ABS wheel sensor as the tell tale light on the dash had been on constantly. I have since put 100 trouble free miles on the clock and as I was pulling into the drive yesterday the ABS tell tale started to flash this time . I did turn the ignition offf then on again in the vain hope that it may reset the system but no luck. I have also pumped the pedal about 30 times with the ignition on to discharge the system but still no luck. Havn't got the manuals out yet, but does anyone have any thoughts?

Graeme.

[bzguy]

I guess some dirt within the ABS pressure switch ? I do have the same problem, still need to check it out ....

[fflyingdog]

Yep unfourtunately it does sound like your pressure switch has gone south,you could try removing it and giving it a clean as someone did on a previous thread. the opnly company that i have found that may be able to help is called http://www.pvl.co.uk/ what you need to do is tell them the upper operating limits and lower operating limits, the switch activates the pump at 2200 psi and shuts off at 2700 psi, they can then factory set them and send you a switch which you can try (you will how ever need to cut your old plug off and splice in a new connection,the guy i spoke to was very helpfull and i think costs about 70 quid (but dont quote me)

Cheers

Nick S4s

Edited December 24, 2008 by fflyingdog

[bzguy]

the most difficult of that all is to find a key that's 1.5 inch (about 39 mm) wide (a 'pot' thing, don't know how you call them)

they sell them up to 32 mm, guess I'll have to ask my local car dealer for a bigger one ...

//edit : found this on internet :

'The GM PART # 88927272 you referred as the switch is really

Brake Master Cylinder Proportioning Valve and still shows available

for $65.21 from http://gmpartsdirect.com/ '

worth a try if you need one ... ?

Edited December 24, 2008 by bzguy

[gumin]

Thanks guys. I had the pressure switch replaced a couple of years ago, so I will give cleaning it ago and see what happens.

[tjs98jetta]

My flashing ABS warning light was cleared up after I methodically cleaned the contacts in the connector to each wheel sensor. Its worth just reseating each one just to see.

Good luck,

Trevor

[gghc87]

Had a simliar problem on the S4S recently. Turned out the bracket that held one of the wheel sensors in place was cracked and so sometimes the sensor worked and other times not. The result was the sensor would sometimes active on the road so the system was sensing sudden and massive acceleration, some would say normal for an S4S , and the system kept giving false readings, turning the tell tell on then off then on for no reason.

All fixed now

[bzguy]

Went for a nice rip today, but when I came back, the BS pump remains running ; only way to stop it is disconnecting the battery :S

Had the ABS tell tale light flashing/steadily on already for a while (intermittent), but didn't have the chance yet to disconnect the pressure switch (I suspect dirty r broken pressure switch)

Does anyone know (picture if possible) where the ABS pump relay is located ? It's an 1994 S4 LHD. And where is the ABS pump fuse ?

Maybe it's a sticky relay, or pressure switch ...

Thanx

//edit : it's a miracle !

I disconnected/re-connected the pedal sensor, I removed the 15Amp and 30Amp solenoid fuses, cleaned the contacts and put them back and ... brakes work like never before, really great now, and all tell tale lights are gone, pump stops running etc etc ... fingers crossed that it just was some bad contact ..

Edited April 5, 2009 by bzguy

[NIJ]

Guys- this may sound like a daft question, but when the ABS light comes on does it disable any thing else?.

The reason i ask is i have a strange electrical fault - every now and then the ABS light comes on and at the exact moment this happens the power goes off to the internal fans, the engine cooling fans and the air con. Then when the light goes out the power comes back on again to the fans etc.

this happens on and off whilst driving or somtimes when starting the car.

when all is well the ignition is turned all lights come on for the check - you then hear a buzz noise (like a relay) then all go out and every thing works as normal

But sometimes however the buzz noise does not happen and the abs light stays on and the fans do not work etc

have been thinking that it maght be an ABS relay failing from time to time?????????

any help would be greatly appresiate

[bzguy]

blinking ABS light means that there was a fault, but ABS is still working

Steady light means something is wrong and the ABS is disabled ; just the ABS, nothing else ; off course 'normal brakes' still work

BTW : ha dmine checke dout, since ABS pump was running again constantly : it was a sticky pump relay ...

[htiek]

Guys- this may sound like a daft question, but when the ABS light comes on does it disable any thing else?.

The reason i ask is i have a strange electrical fault - every now and then the ABS light comes on and at the exact moment this happens the power goes off to the internal fans, the engine cooling fans and the air con. Then when the light goes out the power comes back on again to the fans etc.

this happens on and off whilst driving or somtimes when starting the car.

when all is well the ignition is turned all lights come on for the check - you then hear a buzz noise (like a relay) then all go out and every thing works as normal

But sometimes however the buzz noise does not happen and the abs light stays on and the fans do not work etc

have been thinking that it maght be an ABS relay failing from time to time?????????

any help would be greatly appresiate

This rings a bell!

When I first got my SE, occasionally just after starting the engine ABS lights on and no heater fans. Usually it would sort itself out after a few minutes, on other ocassions I had to switch off and re-start.

Like you I suspected a relay so took the highly technical approach of pulling every relay (front and back compartments) and giving all the contacts a clean. One relay at a time I hasten to add! The problem has never come back.

When I finally got a workshop manual I had a brief perusal of the electrical schematic and think the most likely suspect is the 'start drop-out relay'. This looks to feed the heater fan switch and ABS control circuit amongst others. As my problem has not re-appeared (touch wood!) I haven't investigated further so I stand ready to be corrected.

Attached are what I think are the relevant pages...

MK_Electrical_90MY_on_sheet2A.pdf

MK_Electrical_90MY_on_sheet30A.pdf

Cheers,

Keith

[NIJ]

Thanks Keith - that seems to be the most logical reason.

Last night i did as you had and pulled out and cleaned all the relays and fuses etc (none were really dirty though) and also took a new fused power supply from the battery to the radiator fan sensor (by passing the ignition and all other of the cars wiring sytems), so hopefully if the problem happens again at least the radiator cooling fans should not be affected.

All was ok again last night, but this fault has been intermitant so am not sure if the cleaning has fixed it or not. Guess time will tell!

The start drop relay as you say looks to be the problem espessially as when ok i can hear a relay click about 4 seconds after ignition on and when the fault occours this relay click cannot be heard. Think i will try and replace this relay anyway

cheers Nigel