Ok lets dismiss a few things first. The OVP protects computerized equipment, when it goes it affects the ECU, ABS, and a few other systems. But not the lights or wipers. The only valid test for an OVP is substituting a good OVP, I dont care what it says in the FSM or in misleading internet chatter. Second, if the alternator has been replaced withnew, the odds of having bad brushes is small. I think this is being caused by a bad main ground strap or loose battery cable.