coupe quattro 1989 ABS

[sox]

Hi all,

my 89 coupe quattro b3 seems to have developed a small quirk that im not sure how to handle. Pretty sure its electrical.

The car has switchable ABS. when the button on the console is pressed the abs is enabled and a small orange light apeers on the dash.

The light on the dash is on all the time now and wont go away, regardless of whether the abs is actually on or not.

Has anyone got any idea????

Tar

rich :confused:

[scotty33]

Seems like symptoms of a bad ABS relay : (last paragraph)

http://www.20v.org/brakprob.htm

[jonw85]

I seem to be having the opposite problem with mine! Had MOT yesterday and it failed on ' Anti lock braking system warning lamp does not illuminate'

Would this point to the same abs relay under the dash?

As its the quattro version it has diff lock which works fine, but the ABS seems to be intermittent. The tester said it worked once and then locked up the front wheels the second time he tested the brakes. ABS switch on the dash clicks a relay when pushed in and out but nothing lights up anywhere. Is the switch meant to light up when pressed or is it meant to just light up on the dash?

(sorry to hijack your thread but we may have similar problems!)

[scotty33]

Hi,

The switch itself is meant to light up, but it is common for these switch lamps to fail.
When the ABS is turned off, the ABS light on the dash should also come on.
The ABS lamp on the Dash should also come on when the ignition is turned on, sounds like you have a lamp out/ (removed) due to a possible problem with the ABS. e.g a sensor problem would make the ABS fail and also should bring the ABS dash lamp on.

This may be of use?:

http://www.sjmautotechnik.com/trouble_shooting/brake.html#ABS

[jonw85]

Thanks. As you said - someone had removed the abs dash bulb. However, I put another in and It works perfectly! Have bought another switch as the bulb holder in mine is broken and I'll give the wheel sensors a clean up though just to make extra sure everythings ok.

Thanks a lot for your help.

[quattrothedog]

I'm having the opposite problem with my Coupe.

Any advice gratefully received.

Just bought it, the previous owner said the light used to come on, but then just stopped.

the switch does nothing either.
Got 12v at the switch, but pushing it seems to make no difference to any of the readings.
The brakes do feel a little spongy, but IDK if this is related ? :Blush2:

Ideas anyone ? :beerchug:

[scotty33]

I'm having the opposite problem with my Coupe.

Any advice gratefully received.

Just bought it, the previous owner said the light used to come on, but then just stopped.

the switch does nothing either.
Got 12v at the switch, but pushing it seems to make no difference to any of the readings.
The brakes do feel a little spongy, but IDK if this is related ? :Blush2:

Ideas anyone ? :beerchug:

So are you saying the ABS dashlight does not come on when the ignition is first turned on? If so, would have to suspect bulb failed or removed.

switch illumination failure is common, with the ABS lamp in the dash also not working, there would be no indication that the ABS has been turned off.
The ABS switch operates through a relay which could also be at fault

http://www.20v.org/brakprob.htm#caliper

[quattrothedog]

Yeah, the abs light doesn't come on at all.

I only picked up the car at the weekend, so I've not had a proper look at it yet, planning to do it over the next few days, but it helps if you know where you're looking !

I found the relay, and it seems to click when the ignition is switched, the fuse is OK, as is the main fuse.

I'll have a look and see if he's taken the bulb out, and I'll have a look at the rings and sensors, give them a little clean up. gonna be taking the wheels off to check the car over anyway.
Being a Coupe, I'm fully expecting to have to put wishbone bushes on it !! :rolleyes:

When I push the ABS switch, nothing at all seems to happen. Pushing the foglight switch etc results in it catching, and staying partly retracted, then it pops fully out with another push.

My ABS switch doesn't seem to "catch" when pushed, is this normal ?
I've had Audi's on and off for years, but never had one with switchable ABS, so I've no idea how it's meant to feel !!!

Cheers.


So are you saying the ABS dashlight does not come on when the ignition is first turned on? If so, would have to suspect bulb failed or removed.

switch illumination failure is common, with the ABS lamp in the dash also not working, there would be no indication that the ABS has been turned off.
The ABS switch operates through a relay which could also be at fault

http://www.20v.org/brakprob.htm#caliper

[quattrothedog]

OK, checked it today. As I suspected, the bulb had been taken out.
The bulbs in the switch had blown too.

checked the fuse at the relay, and everything seems in order, so now I'm stuck with the ABS light on all the time.

Opinions gratefully received, should I start my diagnostic hunt by replacing the relay first ? :1zhelp:

Cleaned up the back rings, but not the front. I'll get them at the end of the month. I'll pop the shaft when I do the bushes. The previous owner must have slept with his MOT tester. Can't believe how bad they are !! :aargh4:

[scotty33]

I think if the lamp is on straight away, then there is a problem with the system i.e a sensor could be shorted or open circuit or a modulator/ECU problem. If the relay was stuffed, It says in the 20v link, the fuse would blow so I guess not the culprit?

Starting point is to meter the sensors, should be approx 1200 ohms across the 2 wires from each sensor, also check they are not down to earth. connector plugs for the fronts are by the airbox and expansion tank, rears probably under the seat (they are on a 90)

[quattrothedog]

Cheers, I'll have a look at that. :D


**Edited** After looking at it today, the relay's working fine, all the sensors read around 1200 ohms, give or take, except the front right.
having difficulty sourcing one, except from a main dealer, which is £155 !! :(

SinceI'm not 100% sure that's the problem, reckon I'll just try to get a hub, complete with sensor, from a scrappy. The wheel bearing is a little noisy on that side anyway.
Still nothing from the switch, it looks like it might be broken too, I can switch the relay manually, but we'll see once it's done.

thanks for the help.

I think if the lamp is on straight away, then there is a problem with the system i.e a sensor could be shorted or open circuit or a modulator/ECU problem. If the relay was stuffed, It says in the 20v link, the fuse would blow so I guess not the culprit?

Starting point is to meter the sensors, should be approx 1200 ohms across the 2 wires from each sensor, also check they are not down to earth. connector plugs for the fronts are by the airbox and expansion tank, rears probably under the seat (they are on a 90)