1993 W124 E220 TE (16v) OVP

[teddycatkin]

Can anyone point me in the right direction as to the correct OVP relay for my car ?---had it 2 years now no problems -but last week ABS light came on -went on and off by itself for a few days -now on all the time --The OVP fitted is part number 000 540 67 45 --it has 2 slots for fuzes in the top with one 15v blue fuze fitted in left side as you look at it from the front.--is this the correct part number ? if I need to get another one.
I see several advertised for W124's but with slightly different numbers --
ie-- 201 540 37 45 ? are they interchaneable?
I cannot see any problem with it at the moment and am waiting to borrow a mb diagnostic tester to try and trace the problem.

 

[television]

The only OVP relays sold now are the 9 pin versions and they come with a blanking cover for the pins not used.

Pin 30 has 12 volts on it and pins 87 should have the same voltage, on later cars this can be measured on pin 30 of the engine ECU or from the access holes in the fuse on top

 

[roofless]

you could place a wanted ad here http://forums.mercedesclub.org.uk/forumdisplay.php?f=9 you might get what you need asap

 

[brianbrian]

Try Robparker123 he is on the forum only breaks mercs,

 

[teddycatkin]

ovp

The only OVP relays sold now are the 9 pin versions and they come with a blanking cover for the pins not used.

Pin 30 has 12 volts on it and pins 87 should have the same voltage, on later cars this can be measured on pin 30 of the engine ECU or from the access holes in the fuse on top

I have contacted my local stealer and the original part number is correct and still currently supplied on the MB parts list ??(£60+)?--the ovp has one single 15 amp fuze - the fuze and relay and all wires to sensors seem OK and the engine ticks over and runs and starts fine--just the abs -light permenantly on ?? What do I check next?

 

[wireman]

Get somebody to open your OVP and closely examine to soldering on the PCB oard, odds on one of the PCB mounted relay terminals has a dry joint.

There is next to nothing in the thing, just a few electronic bits on a board.

Opening the unit is the tricky bit since you should seal it after the jobs done, I have with some success cut off the ali can across its corners and left four sides untouched and unattached from each other so it clips back together (with some silicone to assure the seal). Take the fuse out before you try to extract the gubbins or it wont come out.

good luck

 

[kth286]

Voltage level is the important thing so maybe your battery is getting weak - have it tested
or charge it up.

 

[television]

And why not a sensor fault, any simple diagnostic gear will find that

 

[wireman]

The voltage level bit may be a red herring, the bosch ABS sytem will function correctly at a power supply voltage of 10.5 to 14.5 volts.

Within the ABS control unit a feed is taken out to energise the OVP relay coil, this feed is dependent on the applied power being greater than 10.5v which would if it was the battery/alternator at fault result in very dim lamps etc and the obvious presence of a power fault, like the starter wont turn and the car wont go etc.

The OVP has two functions and contains two circuits to perform them.

For over voltage protection of the ABS electronics (and in some cases other electronic modules) a large avalanche diode (Vbr~19v) is fitted across the incoming 12(14)v supply and if a large load dump (Vbatt>19v) event occurs (battery disconnect or alternator regulator fault) whilst the thing is powered it will blow the 15A fuse and prevent expensive damage to the ABS pump and the power circuits in the control electronics.

The second circuit is a low (<10.5) voltage detector which in the event of alternator loss or dead flat battery will prevent the ABS from attempting to help out with skid control (if needed).
The low voltage detector is in the control unit, the relay it operates is in the OVP, the relay contacts provide 12v power from the OVP fuse to the control units power output stage and the pump units relays (along with any other non ABS control boxes that require protection).

Why have under voltage protection?

The control current in the soleniod valves is modulated to one of three levels, off, 1/2 and full to setup the normal, ABS hold and ABS return phases of the ABS control cycle, the 1/2 current pressure hold phase requires that the voltage applied be within the range of 10.5 to 14.5 volts and if that is not the case the hold function will be impaired and the ABS will hinder rather than help skid control.

This information (applicable to ABS2 and ABS3) is contained in the Bosch automotive handbook, one of the best quick reference books I posess.

 

[television]

When a car fitted with an OVP relay, if the voltage is exceeded to the 19volt, the Zenor diodes (2 off )can go short circuit. under normal overloads, the output on any pins 87 will fall to 7.5 volt when the fuse has blown.

On cars with ASR and ASD these use the 9 pin versions, the two extra outputs, separate from the normal pin 87 drive these 2 circuits individually.

A voltage check on pin 30 of the ABS pump should give the answer.
Many MBs after 1991 use the OVP relay to safeguard the engine ECU (motronic) when the OVP relay is at fault you have the ABS light on plus the engine will be rough at idle

 

[teddycatkin]

New Bosch silver H/D battery fitted 3 months ago ?

 

[teddycatkin]

Today I removed relay --changed fuze -which was ok and squirted wd40 in terminal where it plugs in --started car drove to the end of the lane 500 yds (ABS still on ) braked and it went off ? drove it on 3 short trips this afternoon and its still off ?? all seems back to normal -should I buy a new relay just in case--? I am worried now what has caused this -should I remove the ABS sensors and clean and check them and the reluctor rings anyway?

 

[wireman]

Cleaning up the sensors and rings would be a good idea, make sure that the cables do not get stresed whilst you fiddle with them and use locking compound on the retaining bolts on assembly.
I'm still for the OVP relay being dodgy it took several attempts at diagnosing my car untill I finaly cut the relay open and under very close inspection found the dodgy connection, Malcolm you put me on to this so my thanks to you.
To date I have found 1 sensor and five OVP (poor soldering) faults on several older 201 & 124 models suffering from intermittent lamp on syndrome.

 

[television]

Cleaning up the sensors and rings would be a good idea, make sure that the cables do not get stresed whilst you fiddle with them and use locking compound on the retaining bolts on assembly.
I'm still for the OVP relay being dodgy it took several attempts at diagnosing my car untill I finaly cut the relay open and under very close inspection found the dodgy connection, Malcolm you put me on to this so my thanks to you.
To date I have found 1 sensor and five OVP (poor soldering) faults on several older 201 & 124 models suffering from intermittent lamp on syndrome.

The OVP relays made in Austria are the worst for dry joints, the Irish versions are better.
Fuel pump relays go the same way, and on all MB's if no kick down, then an open circuit track on the fuel pump relay PCB where fitted

 

[teddycatkin]

OK Guy,s-Latest on relay saga-for the last two days it stayed off !
Went for petrol this morning waiting at the pumps at Morrisons with foot on brake pedal ( its an auto )and on comes the ABS light again.?? its stayed on again now today.
From all the advice now given -I am thinking it has got to be the OVP relay--weak or broken soldering in joints--I will attempt to remove it and check and solder if needed tomorrow!!! and report progress.
As I quoted earlier the relay fitted is 000 540 67 45 ( made in Hungary ) with one 15 amp fuze in top is still available from mercedes at £60 + vat -- I cannot find anyone else selling the same part number --a couple on Ebay ( uk)for £20 -look the same but are different numbers so I dont know if they are interchangeable?
They are however on Ebay in USA for $40-$50 Half the UK price but its the post thats high ? Why are mercedes genuine parts ALL so much cheaper over there? UK prices rip off again! Another interesting point--about my W124 22TE was both the local garages could not find a plug in to test the problem ?? looking from the front on the left side of the engine bay is a big oblong L shaped box lifting the lid it has a lot of numbered terminals showing ?-- another plug (round) on the right hand side below battery has a wire seal on it the MB on --None of us seem to know what this on is for ?? Teddy

 

[television]

The large round lid has the 38 pin diagnostic socket under it

 

[roofless]

this is my spare ovp relay open to show the board very easy to do

 

[teddycatkin]

Malcolm --Sorry for being so thick -Is this the one with the MB wire seal on abou the size of a 50p? its numbered 1 to 7 on the outside ?
The one one left (L shaped ) is numbered 1 to 16 inside terminals what is that one for then?

 

[teddycatkin]

Nice one roofless--I will be on it tomorrow!!!!

 

[kth286]

do not touch the small round plug, it is the fuel trimmer for low octane fuel.

The diagnostic plug is the 16 pin oblong one.

It just needs a simple flash code reader, but the knowledge is what the readout means from a printed list.

You need someone that specialises in your generation of Merc.