Let’s get this clear. There is no effective test for the OVP relay. I don’t care who posts what here, and I don’t care what may or may not be in the FSM. There is no effective test. If you have symptoms related to the OVP, substitute another unit.

As to whether it’s over current or over voltage regulation, it’s both. Primarily it’s there for overviltage protection (thus the name). This may be accomplished with a zener. While you can test the blocking ability of the zebra as mentioned above, testing the breakdown voltage would require isolating the diode and using a variable voltage power supply.

As for over current protection, the OVP is one of several relays that is incompetently placed in an unfused power source. In order to protect the wiring harness, it has one or two ATE fuses in the lid. If one of these fuses blows, it may indicate a short in a downstream circuit. It may also indicate an internal short. The OVP would be suspect in either case. The peculiar mounting for these fuses can also cause intermittents.