Regulator issue if at 18 volts?

My 70 Swinger had that issue last summer. I was driving it and evrything got real bright. The volt guage was pegged on the charge side. After awhile it did just the opposite. Went to the discharge side and everything got dim. The car still ran but I shut it down so as not to have any wiring issues. Got it home and opened the hood to find that cider like sticky crud leaking out from the bottom of the regulator down the firewall. I put a new Advance Auto Parts regulator on the car and the problem was gone right away. Good Luck!!
Chas.