W124 ABS light - It's The OVP Relay but why?

[richip]

After bringing my 124 E320 out of hibernation I found that the ABS light stayed on. I searched the forums on this excellent site and realised that it was probably the OVP relay.

I charged the battery and checked the 15amp fuse on the top of the relay but neither solved the problem. I then removed the OVP relay, opened the case and prepared for some soldering.

On inspection I noticed that the clear plastic inner shield had some burn marks next to the smaller coil. Parts of the coil itself appeared to have changed colour due to burning.

Is this just a general failure - the relay looks to be the original item (000 540 6745) or should I be looking for another problem before I replace it?

I'd very much appreciate some advice.

 

[television]

Are you sure that it is not just the dry soldering around the base of the relay

 

[grober]

The ABS Unit, the motorised idle speed regulator and the engine ECU are all fed from the OVP. If the voltage supply to the ABS unit falls below a certain set value [ thus presenting the hazard the ABS unit may not operate correctly] the ABS warning light comes on. Restore the supply to 12V and the light will extinguish.
The fault can occur simply by an increased voltage drop across the relay due to poor connections[ internal or external] . The OVP will continue to work to certain extent rather than fail making fault finding difficult.
If its the original relay = 14+ years old I would be inclined to replace it? although resoldering the contacts as Malcom says may well cure it

 

[richip]

When I opened the case on the relay I was expecting to find a dry joint. Before I noticed the burn marks I ran a continuity test from each pin back to the solder joint on the PCB. They all seemed to be OK. It was only then that I started to look for another problem and found the burning next to the smallest of the three coils.

 

[Wirral_guy]

What does this smaller coil do?


If it is an energiser coil (to turn relay contacts on or off) it may just be energised for long periods at a time at close to it's rated current. The coil gets warm (hot-ish) enough to leave scorch marks on the shield....

..or...

...there may be a very slight nick in the insulation of the coil wire that, in damp conditions may cause a spark jump (this option may also explain the failure after being laid up for some time - slight condensation in the shield making the air a little damp, causing a spark jump type short and triggering the failure).

Difficult to be certain (i.e. I'm guessing :lol without seeing pics of the damage.

Either way, unless expensive, I would just replace the OVP, especially if it is 14+ years old.

Dave

 

[richip]

I think I'll bite the bullet and buy a new relay although I will keep the old one and have a bash at re-soldering it. Thanks to everyone for their help.

 

[richip]

Fitted the new OVP unit this afternoon and the ABS light went off without delay. Happy days.

 

[balddaed]

OVP relay question

Greetings to anyone out there ...a quick question about this relay question; I'm having a similar starting problem....cranks over nicely but wont light up. Just started happening, luckily it happened in my garage rather than some shopping mall. So just how do you remove the part? Does it pull straight up or out to the side. I dont want to damage any contacts or prongs. Appreciate the advice! Thanks, Ed in Topeka

 

[maska]

Ovp

Fitted the new OVP unit this afternoon and the ABS light went off without delay. Happy days.

Hi; These relays are a real PAIN in the ARSE ; I tried THREE; before I found one which was Reliable. :neutral:

 

[grober]

Greetings to anyone out there ...a quick question about this relay question; I'm having a similar starting problem....cranks over nicely but wont light up. Just started happening, luckily it happened in my garage rather than some shopping mall. So just how do you remove the part? Does it pull straight up or out to the side. I dont want to damage any contacts or prongs. Appreciate the advice! Thanks, Ed in Topeka

The connections are pretty robust --cylindrical pins on the base of the relay on to a fixed base. usually the relay can be removed by combination of pulling upward while applying pressure side to side =wiggling it a bit. Sometimes there's a cover to be removed first and in some set ups the relay is mounted by 2 small bolts to the bulk head and its a moveable wired socket that just plugs on to the base.
#
Having said all this you don't say what car you have. The relay which tends to effect starting may be the fuel pump relay rather then the OVP

 

[television]

The fuel pump relay can be checked by removing it and bridging out pins 7 and 8 in the socket, then the fuel pump will run all of the time that the ignition is on for testing

 

[balddaed]

OVP repair?

My vehicle is a '95 Cabriolet..has 140 K..still won't start. All fuses are good; newer battery, fuel pump relay is tested good. Just pulled the OVP realy to check the internal solder parts. But can anyone tell me how to safely open the case?Do I flare out the metal at the base or try to remove the white plastic top that holds the fuse? Maybe I should just buy a new one? But I love doing my own work; last year I pulled the cylinders thata operate the electric top.....lots of grunting on that job. Thanks for anyones help.

 

[television]

The OVP relay will not stop it from starting, you must look elsewhere, do you have a spark, pull the fuel pump relay and bride pins 7 and 8 and try

 

[wireman]

I have seen these relays with the same burnt coil, whilst we here are calling it an OVP it is not called that on MB data, engine management relay seems to be it.
The relay switches power to several circuits in the engine management and certainly does stop a C220 from starting when the small relay is dead, take the can of and mannualy hold in the armature and the car will start.
45 quid at ECP.

 

[television]

I have never known an OVP relay to stop a 124 CE320, it can cause poor idle.it is called an OVP relay on the 124, the engine management circuit is here, but not much help as we do not have the main ECU pins.
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM WIRING DIAGRAMS/5418.pdf
The 202 C class mainly do not use one

The OP asked if he could open it up, and indeed he can by just straightening the bent top of the alli case and it will all slide out

 

[kth286]

perhaps the immobiliser is stopping this car starting.

try closing and opening the central locking with the remote a few times - do the green/red
lights operate as they should ?

 

[balddaed]

still looking for a solution

Regarding my '95 cabriolet that still wont start: battery is good, locks, alarm, radio all still work. My top is down but I dont have enough power to close it. When the engine is running, all is fine, great performing car. This "no start" thing started rather suddenly, good thing I was parked in my garage & not at a restaurant out of town.
I removed the fuel pump relay, used a jump wire to bridge the correct contacts & the pumps started to hum. I did not even have the ignition switch on. Should I use the jhump wire & try to start it? I also managed to open up the OVP part, saw no solder breaks etc, & reinstalled it. The engine turns over very strong; just never lights up. How do I check for a spark?
Thanks to all that are following this.
PS....my wife is the frequent driver of this car; now she says if it ever gets running, she will never trust it again & it will be for sale ! Help !

 

[television]

Yes you should try and start with the fuel pump relay out and the pins bridged.

Re the spark, you can buy in line spark testers very cheap

 

[balddaed]

Thanks again for your advice.....just tried using the jump wire while my wife turned the key...nothing different ; engine did not light up.
Looks like I will start the spark tests.
Thanks again.

 

[balddaed]

Old story & new question

FYI to whomever helped me with my no-start problem on my '95 Cabriolet. Spoke to a benz mechanic in nearby KC; suggested replacing out the OPV relay...I did & now it works!. Actually a very easy fix.
But now another quiz/problem for anyone. While driving at night with the headlights on I recently noticed that I do not have any brights. Low beams on both lamps are fine, but when I depress the turn signal stalk to go to brights nothing happens.
Any " bright" ideas out there?
Thanks !