I don't remember what I did for mine....I think I got the headlamp motor off of a 70-72 C body. I pulled the plastic gear inside and the bulkhead and re-soldered all the connections on the motor itself. They were all badly corroded, so I sealed with electrical tape paste and heatsinked everything. I believe the connector was the same one used on the front valance turn signals which I eventually took out and replaced with GM weather-tite connectors. Like I said...been about 8 years since I played around with that motor...grease the heck out of the gear when you get it working with graphite lube. I even made a plexiglas sheath to encapsulate the motor on the front to prevent it from getting wet during rains.

Just out of curiosity....could the headlamp switch be bad? You get juice to the relay when you turn on the lights, but when you shut it off, the lights shut off and it triggers a reverse polarity through the switch and into the relay. If your headlamp switch isn't sending that signal due to corrosion or cratering, wouldn't the switch be at fault. I think I remember my doors being closed, headlamp switch in the off position...and the knob on the bottom of the motor casing was still magnetically energized. The only way to open and close manually was to disconnect the pigtail (weather-tite for me). If you don't have the electromagnetic force on the knob, then you have a supply failure