Almost fully restored W124 cab....and I can't be bothered anymore :(

[Celicasaur]

 

[grober]

Agreed looks to be in good nick. Can only suggest a good inspection with a hand magnifier- dry joints can look OK to casual inspection- followed by a reflow of the main soldered joints on the PCB - ???

 

[Celicasaur]

Yeah, my thoughts exactly. I re-tinned all of the joints using my magnifying glass for the hell of it, seeing as I went to the trouble of getting it out of it's casing.

 

[grober]

I'm afraid the only other action now is substitution/ replacement. The OVP relay is based on zener diode technology which rarely goes wrong as most of the time its not brought into play. the most common fault is dry joints but sometimes the relay contacts become burnt and too resistive allowing voltage to drop- In which case substitution is the only effective test left if indeed the OVP is faulty.
Excellent writeup here.
OVP Relay Tech details

 

[Celicasaur]

Ahhhh, I just figured that the ABS light might also have been because of the sensors needing a clean, which I'll need to get around to. If that doesn't help the issue, then sure, I'll just buy a new OVP. I'll add it to my huge list of parts that been replaced on this car, hehe...