Your regulator should have 2 plugs. One with 2 wires and one with 3 wires. Disconnect the 2 plugs. Set your meter to Ω. Set oen lead to the frame use the other lead on each wire on the 2 plugs. Make sure your testing the wires that go into the engine, not into the regulator. On the plug with 3 wires you should get infinity or OL on your meter on all three wires. On the plug with 2 wires the red wire should give you infinity or OL. The black wire should give you a very low resistance, e.g. 0.3Ω. You are checking to see if a wire has rubbed through and is contacting the frame.