GROUND The VR MUST be grounded and at same voltage as battery NEG. To check this, run engine at simulated low/ medium cruise RPM, and check first with all loads off, and again with lights, heater, etc, powered
Stab one probe into the top of the NEG battery terminal, and stab the other into the VR mounting flange. Again you are looking for a very low voltage, the lower the better, zero is perfect