Mercedes-Benz Owners' Forums  

Go Back   Mercedes-Benz Owners' Forums > Technical > Suspension, Steering & Brakes
 

Reply
 
Thread Tools Display Modes
  #1  
Old 02-08-2012, 09:03 AM
sladedestiny sladedestiny is offline
Junior Member
 
Join Date: Aug 2012
Location: Bournemouth,UK
Car: 300e,1991,3litre
Posts: 1
Arrow 300E 1991 Mercedes. The ABS light stays on perminantly

Hi.I have just joined.I an trying to get help with a problem on my 300E 1991 Mercedes. The ABS light stays on perminantly.I have checked relays( including the constant voltage one with the fuse on top) all appear ok. sensors look ok although I have not taken them out or cleaned them..So I have no ABS brakes.Any pointers would be great.
Reply With Quote
  #2  
Old 02-08-2012, 09:09 AM
television's Avatar
television television is offline
Senior Member
 
Join Date: Mar 2005
Location: Daventry
Car: 2002 SL500, 216 CL500, all fully loaded
Posts: 163,814
Default

Quote:
Originally Posted by sladedestiny View Post
Hi.I have just joined.I an trying to get help with a problem on my 300E 1991 Mercedes. The ABS light stays on perminantly.I have checked relays( including the constant voltage one with the fuse on top) all appear ok. sensors look ok although I have not taken them out or cleaned them..So I have no ABS brakes.Any pointers would be great.
Re the OVP relay with the fuse on top,,,the only way to check it is by measuring the outputs on all pins 87 on the relay, you cannot do this in situ without a break out box. the other way is to check that you have 12 volt driving the ABS ECU

A simple blink code reader would help you find the fault
__________________
Malcolm

Don't worry, it only seems kinky the first time
Reply With Quote
  #3  
Old 02-08-2012, 09:10 AM
whitenemesis's Avatar
whitenemesis whitenemesis is offline
Senior Member
 
Join Date: Dec 2006
Car: CLS55 AMG '05
Posts: 17,982
Default

You may have been trying to post in the DIY section. No permission for users there.

I have moved your post out of the FAQ .
__________________
CLS55 AMG
C270 CDI - Gone but not Forgotten
Reply With Quote
  #4  
Old 02-08-2012, 10:27 AM
Alex Crow's Avatar
Alex Crow Alex Crow is offline
Authorised Forum Supporter
 
Join Date: Jul 2009
Location: Super Suffolk
Car: W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
Posts: 10,675
Default

I don't believe there was ever any diagnostic fault code facility in the 124 series ABS systems, unfortunately.

AS has been said, it is usually an OVP or wheel speed sensor, and these should be tested with a meter - a visual check is pointless.
__________________
ALEX CROW - Independent MERCEDES-BENZ Specialists
Reply With Quote
  #5  
Old 02-08-2012, 10:47 AM
television's Avatar
television television is offline
Senior Member
 
Join Date: Mar 2005
Location: Daventry
Car: 2002 SL500, 216 CL500, all fully loaded
Posts: 163,814
Default

Yes you are right, only on the 124034 and 036 with the 38 pin box
__________________
Malcolm

Don't worry, it only seems kinky the first time
Reply With Quote
The Following User Says Thank You to television For This Useful Post:
Alex Crow (02-08-2012)
  #6  
Old 06-08-2012, 06:08 AM
wireman wireman is offline
Senior Member
 
Join Date: Sep 2005
Location: lancashire
Car: nice 201 2.5D 1993 & very nice 129 SL500 1994
Posts: 2,632
Default

In my experience with ABS the OVP is a the most frequent culprit.

!2v is supplied by it to the ABS control and hydraulic units (OVP pin87, red/yellow wires), on petrol models it also supplies 12v to part of the injection system (OVP pin 87E, red/yellow wires). 12v power arrives at the OVP on a red wire at pin 1.
!2v ign on power arrives at the OVP pin 6 on a pink/red wire.

The red/yellow wires from pin 87 go to pin 1 of the ABS control and pin 10 of the ABS hydraulic units. Pull the plug on the hydraulic unit and look for 12v on pin 10 (ign on). Pins 6 & 12 (red wires) of this plug are hot all the time, I think directly from the terminal block in front of the battery.

Check all the brown earth wires for integrity and freedom of corrosion at the body studs.

The sensors can be at fault, if the warning occurs as soon as you switch on an open circuit in any of them will cause a fail.
The rear sensor connects to a terminal block beneath the rear seat on the right hand side, blue and yellow wires are connected to it, lift them and check for 500 to 2000 ohms between the ones that disappear towards the axle.
The front sensors are connected by coaxial plugs near the top of the suspension turrets under the bonnet, pull the plugs and test for 500 to 2k ohms.
The sensors should generate more than 100mv AC when a wheel is spun by hand, this test would only be required if the ABS lamp comes on as you move off.

My bet is the OVP relay, they can get dodgy due to poor internal connections which can be repaired by a deft hand and soldering iron. Giving the OVP a sharp tap can sometimes put them back into order but it will fail again.
Europarts stock the relays for about 50.

You might try as a temporary measure bypassing the OVP by linking pins 1 and 87&87E of the OVP socket, if it works its definitely the relay to blame, don't operate the car like this, there will be no circuit protection and your battery will go flat if its left any length of time.

Welcome to the forum and please do let us know how you get on, good luck.

Last edited by wireman; 06-08-2012 at 06:56 AM.
Reply With Quote
The Following 3 Users Say Thank You to wireman For This Useful Post:
alexanderfoti (10-08-2012), dlicheri (19-01-2017), Stedan 126 (06-08-2012)
  #7  
Old 12-01-2017, 07:12 AM
dlicheri dlicheri is offline
Member
 
Join Date: Apr 2015
Location: london
Car: 190D 1992 2.5D
Posts: 10
Default

Quote:
Originally Posted by wireman View Post
In my experience with ABS the OVP is a the most frequent culprit.

!2v is supplied by it to the ABS control and hydraulic units (OVP pin87, red/yellow wires), on petrol models it also supplies 12v to part of the injection system (OVP pin 87E, red/yellow wires). 12v power arrives at the OVP on a red wire at pin 1.
!2v ign on power arrives at the OVP pin 6 on a pink/red wire.

The red/yellow wires from pin 87 go to pin 1 of the ABS control and pin 10 of the ABS hydraulic units. Pull the plug on the hydraulic unit and look for 12v on pin 10 (ign on). Pins 6 & 12 (red wires) of this plug are hot all the time, I think directly from the terminal block in front of the battery.

Check all the brown earth wires for integrity and freedom of corrosion at the body studs.

The sensors can be at fault, if the warning occurs as soon as you switch on an open circuit in any of them will cause a fail.
The rear sensor connects to a terminal block beneath the rear seat on the right hand side, blue and yellow wires are connected to it, lift them and check for 500 to 2000 ohms between the ones that disappear towards the axle.
The front sensors are connected by coaxial plugs near the top of the suspension turrets under the bonnet, pull the plugs and test for 500 to 2k ohms.
The sensors should generate more than 100mv AC when a wheel is spun by hand, this test would only be required if the ABS lamp comes on as you move off.

My bet is the OVP relay, they can get dodgy due to poor internal connections which can be repaired by a deft hand and soldering iron. Giving the OVP a sharp tap can sometimes put them back into order but it will fail again.
Europarts stock the relays for about 50.

You might try as a temporary measure bypassing the OVP by linking pins 1 and 87&87E of the OVP socket, if it works its definitely the relay to blame, don't operate the car like this, there will be no circuit protection and your battery will go flat if its left any length of time.

Welcome to the forum and please do let us know how you get on, good luck.
Hello wireman,

So if sensors on wheel are open circuit (resistance is infinite) will light be permanently on (from ingnition switch on to starting engine and running )?

I ask as I seem to have this condition on a 190D 2.5 1991. From checking, The only thing that the ovp relay seems to feed is the abs Ecu.

Thx and great write up

Appreciated!
Dean
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
W124 ABS light on, tachometer off wraltd Electrics, Vacuum, Ignition and ECU 18 26-01-2011 10:39 PM
Abs Warning Light - Sl300 129 thewho1971 Electrics, Vacuum, Ignition and ECU 5 27-05-2007 05:53 PM
Sprinter van worn pads light stays on panason1c Electrics, Vacuum, Ignition and ECU 0 19-05-2004 01:16 PM
w124 abs light stephen burton Electrics, Vacuum, Ignition and ECU 6 16-03-2003 11:13 AM


All times are GMT. The time now is 02:00 AM.


Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.