Another bad voltage regulator?

After letting the truck sit for a couple of months, the voltage has started to go crazy high again. I saw 18v at idle with a multimeter connected at the alternator. When I unplug the voltage regulator, or one of the field wires, it completely stops charging. Unlike an A-body, the field wires appear to be green and orange, but they’re old and dirty and I have deuteranopia (color blind). I tried swapping their positions on the alternator and it didn’t change anything. I also took the VR off and sanded the mounting points to clean bare metal on the firewall and the VR itself. Connector pins are also clean and tight.
I tested the voltage at the VR connector and it reads about 1v lower than actual battery voltage.
When I turn the headlights on, the voltage at the alternator output stud dropped to 14.7v at idle.
It has a brand new chineseium VR