[W126 Coupe] Suspect OVP relay (update)

[Vance Rowley]

Yes, at last, confirmed. Received my new OVP relay this morning and before the delivery truck had driven away, I had the parcel ripped open and fitted the relay. My thoughts as I was about to turn the ignition key was "well, here goes" But as soon as I did, I could tell that this is it, as the engine started immediately and the ABS/ASR warning lights went out. It used to take around 10 seconds or more of the engine turning over to start with the old relay. The engine was very smooth and no stumble or hesitation when revving the engine. The idle was fine also.
I know that the OVP gets blamed for everything, but it looks like if you have the 4 symptoms all at the same time.
1. Takes a long time to start
2. High Idle
3. ABS/ASR warning lights remain on.
4. Rough running of the engine.
Then it looks like the problem is almost certainly the OVP relay. Of course it is possible that the fuse is just blown, but if that is OK (as mine was) then a new OVP should be the next step.

For those who want to have a go at repairing the relay, from what I have discovered along with input from this group, it looks like if you get all symptoms at the same time, then as long as the fuse, relay coil, contacts and solder joints are OK, then the most likely culprit is the diode connected between pin# 15 and the relay coil. It is unlikely that the zener diode is the problem, as this would more likely blow the fuse if the zener was at fault. If you get only 1 or 2 of the above symptoms, then a solder joint (or more) would be most likely.But of course when you get only 1 or 2 of the symptoms, say for example the ABS warning light on, then it's possible the OVP is fine and that the problem could be the ABS computer itself. It's understandable that the OVP gets blamed for everything, but is certainly the first thing to check.

Thanks again to everyone who gave their input.

Regards,

Vance.
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