I assume Wales as in the British Isles. This means that all your important relays and computers are behind your battery. There is a plastic cover to be removed. In my 260e there is another small plastic cover over the OVP see fotos. See foto of FPR and OVP relay. You may have the newer type of OVP which has a red top and two fuses. Get the latest variant of the relay to suit your car. M.B. added variations to these relays over the lifetime of using them. This was always a problematic part

http://farm4.static.flickr.com/3046/...768c73e802.jpghttp://farm4.static.flickr.com/3152/...5e69ae5da7.jpghttp://farm3.static.flickr.com/2234/...6c156b586f.jpg

Found it !!!!! Now to test it. In the event that this is not the problem any ideas where else to look...

Many thanks

The only real way to test is to try another in the car.

There is a zener diode in the relay. It goes out of electrical spec.

Result...!!!! Changed the OVP and all is well. For good measure i also fitted new discs, pads and a few other parts but all is now well....many thanks for your advise and help...

Philip:D

ABS light
 

I have a similar issue - abs light on, poor starting and idle and the battery recently died on me and was replaced. I'll try the relay and see how it goes. Hopefully well!

Would this also cause a juddery vibration when accelerating from 40 mph to 50mph? Another recent occurence.

1990 200E

Adrian

Thanks!
 

Thanks to all who mentioned the OVP relay. I swapped one out of my brothers car (1993 200E) and it did the trick right away. Problem solved. Now to order a new one. You lot are geniuses! You saved me a fortune and my car is running perfectly! Thanks,

Adrian

Thanks thanks thanks
 

I recently jumpstart my 300E and after that the ABS light came up :confused:
and the engine was running rough. Oh no i have ruined al the electronics was my thougt ! :eek: after reading the tread and change the fuse on the OVP relay everything is working well again!! :D

thanks

Same problem diffrent car. Funny?
 

Hello! Thank god for you guys whoever you are. My 89 300e has been idlenig low and not wanting to start for a few days now. I was just on the phone with a local mb parts dealer looking for a cold start valve when I came across this thread. Like I said all the symptoms look to me like it could be the ovp. However I have seen some threads that have said it could be the cold start valve. I am ready to fix the problem. Any help would be great!!!!:D

Rough Idle and ABS dashboard light on
 

First off, many thanks to all the contributors! All the information on this thread has proved exceedingly helpful and insightful!

After jump starting my W124 the ABS light illuminated on the dashboard.

And I noted that on turning the ignition the engine was rough on idle.

Following J. Hidalgo's advice I decided to investigate the overvoltage relay (OVP) which is located behind the battery, by the firewall. It's a small metal box with a red "american style" 10 Amp fuse on top.

The fuse had indeed 'blown' and after I replaced it, the problems were remedied!

So many thanks guys! Especially J. Hidalgo!

Ovp relay
 

I have a 91 300 e. It is under a plastic cover between the battery and the firewall. Has a little clear plastic cover with a red 10 amp atc. Fuse in it. I hankie read that some have been able to open them up and resolder bad connections