If johnathan1 is handy with a soldering iron, he could try and pry open the OVP, and resolder the connecting pins. It seems the internal connections to those pins sometimes develop small metal fatigue cracks that cause the intermittent failures. The same also can happen with the Fuel Pump Relay (I fixed mine some years ago), and to a lesser extent to the Klima relay.

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W163 ML230 EURO SPEC 1999
W124 300E 1986