After reseaching the service CD, it looks as though pin 30a is only used on the California version. I'm not sure of it's function though.

Came across some info in a UK MBZ magazine that provides a relatively simple test for an OVP relay that I haven't seen mentioned anywhere else. Did post this info against a recent OVP thread, but was requested to also add it here in-case someone picks this up in a search:

The article is in the Dec '04 issue of MBZ Club magazine here in the UK written by Jeremy Stevens. It states:

"Test 1: Connect pin 30 to a +ve 12v supply and pin 31 to the -ve. Under this condition the only output should be on pin 30a.

Test 2: In addition, now connect pin 15 to the +ve and both relays should operate with supply voltage now also appearing on both pin 87E and 87L (so all pins 'live')".

On my good OVP relay I noted that there was an audible 'click' as power is added to pin 15.

My understanding is this is a fairly basic test: one up from checking the fuses are intact; that it doesn't rattle when you shake it; and that there's no cr@p around the pin connections.

If it fails this test you are pretty sure the OVP needs replacing, if it passes it though, there is still the possibility of an intermittent fault caused by something like a weak solder joint.....