'85 SL280 Over-Voltage-Relay???

[woolf]

Should I have one

I have a permanent ABS light, and can't find 12V at the ABS ECU with the ignition on, only 14V with the engine running.

It sounds to me like the OVP relay/fuse needs checking, but I can't find one. I've identified all the relays behind the kick-board and there's definately not one with a fuse attached.

Many thanks
John

 

[stats007]

From memory some OVP relays are fed from a seperate fused supply - it should be behind the fuse / relay panel in the footwell that you mention - they're silver and slightly larger than the others. On other models the OVPR can be found behind a flap next to the battery - failing that the offside bulkhead under the bonnet if ABS was an option on your 280SL.

 

[woolf]

From memory some OVP relays are fed from a seperate fused supply - it should be behind the fuse / relay panel in the footwell that you mention - they're silver and slightly larger than the others. On other models the OVPR can be found behind a flap next to the battery - failing that the offside bulkhead under the bonnet if ABS was an option on your 280SL.

Thanks for the info.
I had another hunt in the areas you suggest, but found nothing

I think I'll try to order one from my local dealer tomorrow, and see if they can find one listed for my chassis number.

 

[stats007]

Have you tried using this? They offer discount if you don't already get one.

 

[Myros]

just my tuppence worth

I thought I might need an OVP as well for our 85 500. I contacted MB at Oxford with the chassis number, who said ours didn't have one fitted. The German 107 guys I ask for help said there was something up above the fuse box in the kick panel, but i haven't repeated my handstand yet to find it. Perhaps this weekend.

 

[woolf]

I thought I might need an OVP as well for our 85 500. I contacted MB at Oxford with the chassis number, who said ours didn't have one fitted. The German 107 guys I ask for help said there was something up above the fuse box in the kick panel, but i haven't repeated my handstand yet to find it. Perhaps this weekend.

That sounds promising, let me know if you find anything. I'll give you a headstart on the relays I've identified so far. The 4 silver ones are all identical. The 2 together both energise when a door is opened, but they don't control the interior lights.

Thanks for the link Stats007, that looks very useful.

Has anyone ever found a wirinig diagram for one of these models?

 

[stats007]

Is this of use?

 

[woolf]

Is this of use?

Oh yes - very much so!

It lead me on to this page http://www.detali.ru/cat/OEM_MB2.as...=765.701&cat=048&SID=54&SA=+11174&STRK=12#022

which shows the different relay options. Diagram 1 seems to represent my car, and shows it should have a 1165450034 relay in the farm, but I haven't.

I'm now thinking someone has put a standard 0015420219 relay in it's place, which isn't doing the right job.
Question is, which socket

 

[Myros]

Number 5 on this diagram

http://www.sternzeit-107.de/modules...=52145&fext=img&AtchName=Sockel.jpg&AtchNum=0


courtesy of our German oppos at Sternzeit 107

 

[woolf]

http://www.sternzeit-107.de/modules...=52145&fext=img&AtchName=Sockel.jpg&AtchNum=0

courtesy of our German oppos at Sternzeit 107

Thanks Myros, looks like a different layout to mine unfortunately.
I have an "intermitant wiper" relay in that spot, and a few gaps without sockets.
I guess it confirms that I don't have an over-voltage-relay after all.

I just rang my dealer and tried to order one by description, but they said my chassis doesn't have one, and if I have a problem with my ABS I should bring it into the shop :roll:

 

[woolf]

Update, I've swapped around the silver relays, and replaced all the fuses, but the ABS light is still on, still no ABS, and still no voltage at ECU

Surely there must be another fuse or relay outside of the "farm", but I haven't found anything

 

[television]

It is correct to have 13.8volt with the engine running, as it is driven from the alternator and not the battery.

malcolm

 

[woolf]

It is correct to have 13.8volt with the engine running, as it is driven from the alternator and not the battery.

malcolm

Thanks Malcolm, that makes a huge difference to my investigation.
I was under the impression that there should be a battery feed to the ECU as well when the ignition is turned on.

So if I have power, what could be causing the ABS light to stay on all the time? It comes on with the ignition and stays on when I'm driving.

It's starting to sound expensive

 

[television]

if you think about it the ABS light does not go out with the ignition on for the current used would be too high, since when all is OK the ECU starts the high presure pump.Its only when this pump runs that the lamp goes out
With luck your fault will be with one of the sensors on the wheels, the fronts being the most likely. your wheel bearings are magnetic and a hall effect switch does the counting, you could unplug them and clean them. The cables going to them can fracture. A fault code read out would identify the fault.
Looking at the worst the ECU could be faulty though this is not so common.

malcolm

 

[woolf]

if you think about it the ABS light does not go out with the ignition on for the current used would be too high, since when all is OK the ECU starts the high presure pump.Its only when this pump runs that the lamp goes out
With luck your fault will be with one of the sensors on the wheels, the fronts being the most likely. your wheel bearings are magnetic and a hall effect switch does the counting, you could unplug them and clean them. The cables going to them can fracture. A fault code read out would identify the fault.
Looking at the worst the ECU could be faulty though this is not so common.

malcolm

Thanks again Malcolm. I'd ruled out the sensors as they are only capable of showing as a fault when the car is moving and I've checked them all for the correct resistance.

All that's left now is the ECU or the pressure regulator (pump).

Tomorrow I'll check for power at the pump relays.

 

[television]

Thanks again Malcolm. I'd ruled out the sensors as they are only capable of showing as a fault when the car is moving and I've checked them all for the correct resistance.

All that's left now is the ECU or the pressure regulator (pump).

Tomorrow I'll check for power at the pump relays.

OK just remember that the ECU will power up the pump if all is well within the ECU, it used to be the case that outside firms would not repair safety components but these days they will repair them, many people buy one from a wreck for around £100.

when this all started, was it intermitant or did it not work one day.

malcolm

 

[woolf]

when this all started, was it intermitant or did it not work one day.
malcolm

It started not long after I bought the car (I've only had it a month), when I locked up the brakes on a wet road and subsequently discovered the ABS bulb was missing! A previous owner must have removed it to get through an MoT.
I fitted a bulb and it has stayed on ever since.

 

[television]

The main ABS ECU has a built in refference oscillator clock that compairs the speed of the wheels against this clock, should one deviate, then one of the 4 outputs in the ECU operates the valves in the pump block to correct the situation.
Be careful with your asumption that the wheels sensors are not involved with the car at standstill, as the ABS works when all is well at start up, though as the lamp had been removed when you bought it, it would show that someone else had had a go and tried the simple things.
You can run the car without the ECU in the car, so you could ask one of the firms that repair them to test it, the pump and valve block cost in excess of £1k.
If it ended up that way you can drive the car without it, ABS has yet to be proved that it has saved a life, but it does stop small front end damage.
In order to pass the MOT , garages have a time out chart for the ABS lamp, and you could fit a small timer circuit board that turns the lamp out at the required time, cost under £10.

malcolm

 

[woolf]

Should I laugh or cry???

I thought I'd post the solution to my problem, in case anyone else ever has the same "fault".

I had decided to run a separate fused supply to the OVP relay (which turned out to be located behind the glovebox), as it wasn't getting it's proper permanent supply, and I couldn't find it's fuse or source.

So I removed the battery to ease feeding the wire through the bulkhead, and trapped underneath the battery was a wire A wire with a ring terminal that looked like it should be attached to the battery post
A wire that turned out to be the ABS power source :evil:

Evidently whoever changed the battery last failed to reconnect the ABS wire, and subsequently the owner had removed the warning bulb to get it through an MoT.

My local dealer had failed to spot it too, hardly surprising though. At least they had the decency to only charge me for 30 minutes work despite spending 90 minutes on it.

On the positive side, I learned quite a lot about my SL

 

[Myros]

Glovebox hunting I will go then

as the dealers say I haven't one either, and I've looked high and low elsewhere in the car for the little b*gger. It has to be cheaper than replacing all the ABS sensors at nearly £200 each.

Thanks Woolf.