Electrics mayhem

[simon morgan]

I have recently acquired a 1992 300 SL which is now covered 65,000 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 to 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 has now disappeared completely! :lol:

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 yesterday, when accelerating all of a sudden 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 am wondering whether this might be linked either to the ignition key or to some problem between the steering wheel and the column itself which might explain why the electrics seem to work after the S. R. S. light has shone.

Can anybody help me?

 

[pascal]

With all these intermitant problems, I would point to the OVP relay, even though you say it was replaced by your repair man

 

[kth286]

Simon

When you say the voltage regulator was replaced you do mean the unit in the alternator don't you ? and not the OVP relay in the bulk head ?

I would check your fuses. There should be a diagram in the fuse box and go to the obvious ones first (applicable to the problems ie indicators/wipers).

You will likely find the contact points will have a burnt ring around them, so you need to replace each faulty fuse with the correct colour.

Regards

 

[simon morgan]

The garage carried out a fault code test, pin to pin testing of all wheel speed sensors and control units and traced the fault to intermittent low voltage at control unit. They fitted a new voltage control relay. Does this make any sense to anybody as I feel loist when I deal with much more than a bulb! I am trying to avoid a garage spending another 3 hours trying to find the fault.

By the way, can anybody recommend a good independent MB garage near Cardiff, Newport or Gloucester?

By the way the ABS problem returned for about 5 minutes today! I will try all the fuses and report back. Many thanks for the suggestions so far.

 

[pascal]

Sorry I misread your original post and thought you said relay

And now you say

They fitted a new voltage control relay

But are you sure it wasn't the OVP relay (over voltage protection relay)(sometimes called overload relay) that they have just changed this time.

Regarding wiper indicators:
There is a relay in w124s (old EClass) that controls wipers, headlight wipers, indicators & heated rear window. this relay is called a combination relay and as far as i know the r129s one is similar.

 

[simon morgan]

I have changed several of the fuses and will await results. Does anybody know whether the tyre pressures would have an adverse affect upon the ABS system in any way eg sensors? I am trying to decide whether the electrical faults are linked or if it is simply coincidence. :idea:

I will speak to my garage to find out exactly which part was replaced but I took the information in my last message directly from the bill!!