ABS Weirdness

[hnewmark]

Hi there

I have the pleasure of owning a 1983 500SL.

the ABS comes on every time I brake, which is somewhat unnerving, and after driving for about 10 minutes, the ABS light comes on and everything returns to normal ( except of course, the ABS doesn't work at all...).

I have had the ABS sensors cleaned up and then replaced, but this actually made the problem even worse.

Does anyone have any experience of this problem?

 

[paulcallender]

Are all 4 tyres worn evenly (and the same size to start with?) The ever-so-slightly different circumferences of the tyres can cause the ABS to think it needs to function, when it doesn't.

 

[jberks]

Had exactly the same problem on a granada - turned out to be a 'trapped wire' -( read short circuit or broken wire ?) when the garage had changes some bushes. If the signal from one sensor is dodgy then you'll get the effect you see. I believe (though I have no idea how) that you can check the resistances from each sensor at the control unit. If one is off, you have your culprit.

 

[joe bloggs]

Wiggle the leads while checking the resistance, often a poor connection is ok when the car is jacked up and the lead stretched or moved slightly. Not sure what readings you should have, but both fronts should be the same, rear is different.

 

[simon morgan]

I had the same problem on a 1992 300 SL which has now covered 68,000 miles. The first problem was that the ABS light came on and the brakes were then applied but only for a moment. It happened very frequently most particularly over rough ground and at first I thought it might be a sensor in one of the wheels. I took it for repair and they replaced the voltage regulator and they also replaced the right rear indicator bulb. The warning bulb warning light had lit up but I had not linked the two.

For 24 hours everything was well and then during the course of a lengthy journey the ABS light started to come on and off on a frequent basis with the same result that the brakes were applied. It even happened on the motorway and did not appear to be so ground dependent. The ABS light problem then disappeared completely!

I then realised that on occasions none of the controls for the indicators/wipers were working. This included the headlight flash control and I realised that these were all controlled from the same column. This fault was intermittent and the vehicle's electrics would be restored to good health immediately after the S. R. S. light shone for a short while!

Then, when accelerating the blown bulb warning light lit up and the right rear indicator light seemed to have blown again. However, later that day everything returned to normal. Yet later again the blown bulb warning light lit up although the windscreen wipers, headlight flash control and the left indicator appears to be working correctly. The horn has not worked since I bought it.

I still have intermittemt problems with the ABS light coming on. I have solved the other lighting problems. Whenever I start the car I immediately check whether the items controlled from the wiper/light stalk are working. If not, i pull the headlight flash stalk as if flashing the lights. The SRS light shines for a few moments and all, except the ABS light, works perfectly!

Any ideas how to fix both problems permanetly?

Can anybody help me?

 

[Belu]

ABS Problem

Hi Simon,

I had a similar problem on my 1982 500 SEL.
Check the sensor on your rear diff. The wire which seems to be ok and probably passes the continuity test is in fact pulled from inside which while in motion breaks the circuit and causes the ABS to malfunction. Check out all the sensors carefully.

Belu

I had the same problem on a 1992 300 SL which has now covered 68,000 miles. The first problem was that the ABS light came on and the brakes were then applied but only for a moment. It happened very frequently most particularly over rough ground and at first I thought it might be a sensor in one of the wheels. I took it for repair and they replaced the voltage regulator and they also replaced the right rear indicator bulb. The warning bulb warning light had lit up but I had not linked the two.

For 24 hours everything was well and then during the course of a lengthy journey the ABS light started to come on and off on a frequent basis with the same result that the brakes were applied. It even happened on the motorway and did not appear to be so ground dependent. The ABS light problem then disappeared completely!

I then realised that on occasions none of the controls for the indicators/wipers were working. This included the headlight flash control and I realised that these were all controlled from the same column. This fault was intermittent and the vehicle's electrics would be restored to good health immediately after the S. R. S. light shone for a short while!

Then, when accelerating the blown bulb warning light lit up and the right rear indicator light seemed to have blown again. However, later that day everything returned to normal. Yet later again the blown bulb warning light lit up although the windscreen wipers, headlight flash control and the left indicator appears to be working correctly. The horn has not worked since I bought it.

I still have intermittemt problems with the ABS light coming on. I have solved the other lighting problems. Whenever I start the car I immediately check whether the items controlled from the wiper/light stalk are working. If not, i pull the headlight flash stalk as if flashing the lights. The SRS light shines for a few moments and all, except the ABS light, works perfectly!

Any ideas how to fix both problems permanetly?

Can anybody help me?

 

[Belu]

Hi There,

I had a similar problem on my 1982 500 SEL.
Check the ABS sensors on your front & rear ends. The wire which seems to be ok and probably passes the continuity test is in fact pulled from inside which while in motion breaks the circuit and causes the ABS to malfunction. Check out all the sensors carefully.

Belu

Hi there

I have the pleasure of owning a 1983 500SL.

the ABS comes on every time I brake, which is somewhat unnerving, and after driving for about 10 minutes, the ABS light comes on and everything returns to normal ( except of course, the ABS doesn't work at all...).

I have had the ABS sensors cleaned up and then replaced, but this actually made the problem even worse.

Does anyone have any experience of this problem?

 

[piestore]

abs sensor

HI

It is certanly a speed signal fault. the best way is to check each speed signal on scope and make sure all the patterns are correct. Common causes are:-

1 very worn tyres mixed with new
2 incorrect tyre sizes
3 faulty speed sensors or wiring
4 corroded or damaged front hubs (where sensor gets signal)
5 signal ring in diff loose (when hot can spin at any speed)

best bet is check fault codes