Thanks guys,

Yep - it was the OVP. For now, I have actually managed to repair the OVP.

I took the relay out of the car, carefully removed the aluminum cover from the relay body, and started looking around. It didn't take long to find a lot of corrosion at the point where the #30 pin attaches to the bus bar inside the relay. The pin was loose enough that it could rotate in relation to the bus bar.

I managed to clean up this junction and flow some solder back into the joint to get everything working again.

I slid the cover back on, re-crimped it with a screwdriver and small hammer, put it back in the car, and voila - everything works the way MB intended.

It's probably not a good long-term solution, but should hold up until I get a new (to me) replacement OVP relay.

SteveM.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner