Over Voltage with New Battery Disconnect Switch

GROUND......The way to check the ground circuit for this problem is to warm up the engine (VR is voltage sensitive to temperature, or compensated) and run the engine at a "low to medium" cruise RPM, run this test first with all loads off, and gain with all you can power on, radio, heater, lights, etc

Hook one meter probe to battery NEG right at the post. "Stab" the other terminal into the VR mounting flange, being sure to get through chrome, paint, rust. You are hoping for the lowest reading possible, zero volts would be perfect

As in the first harness test, ANY voltage being read here is ADDED to the normal setpoint of the VR. For example, if you read .4V, that is added to a properly working VR, so if it is 13.8, + the .4 will be 14.2. That does not sound bad, except all drops add up, so if you have a ground drop AND a hot side harness drop, you can easily come up with a couple volts!!!!