Here's how this works. You can either measure the drop with the key on and engine stopped between battery and VR, or........
You can measure the difference between actual battery running voltage and the VR power (IGN) terminal while running.
So long as there are no other drops in the system, the above two readings will be the same
This is because The VR regulates the IGN terminal (the sensing terminal) to the VR setpoint. If you have a .3 drop at the VR, then the VR ADDS this to it's setpoint, so that if it is set for 14, the battery "run" voltage becomes 14 + .3 = 14.3V
But the GROUND circuit also must be accounted for, so if there's another .1 or .2 or whatever it might be, THAT also is added. Most of "these old girls" have more than that in the hot harness
Your original circuit path to the VR is this "map" Battery.....fuse link.....BULKHEAD CONNECTOR.....ammeter........welded splice...........IGNITION SWITCH CONNECTOR.........THROUGH THE SWITCH..............BACK OUT the SWITCH CONNECTOR..............BACK OUT the BULKHEAD CONNECTOR
Everything in caps is "likely suspects" and in a few cases the ammeter and welded splice are as well. Many guys on here with overcharging had 1/2 volt OR MORE drop. My own car, right after I bought it "dead stock" was charging at 15.5 volts!!!! It had 1.5V drop in the wiring harness!!!
