In the wiring diagrams it seems more like a load-reduction relay than over-voltage however, it also serves to disconnect sensitive electronics from the alternator when the key is turned off, preventing them from exposure to a "load dump" which can be up to 60VDC reverse-polarity caused by an electric field collapsing in an alternator when switched off etc.
In electronic design for automotive, most electronics are protected from this load dump by MOVs, relays, zener diodes, etc. Basic spike supression or isolation.
Test it like a normal relay-array, the procedure has been outlined by Arthur fairly recently.
Quote:
Originally Posted by cliffmac
and the OVP is VERY OVERRATED and typically not required but very often replaced for no reason at all, other than to garnish profit for the agency repairing your machine.....
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Thanks for weighing in cliff, and wrong as always.
Always required, without it several items such as the tachometer, ABS, ASR, and even the engine module will malfunction or not function.
Fortunately those of us who actually know Mercedes cars know enough to suspect the OVP relay when there are related malfunctions.