When troubleshooting electrical problems, the first thing to do is verify there is a good ground. Bad grounds cause all kinds of bad electrical behavior.
Under the instrument panel, just to the left of the speedometer, there is a big bundle of black wires that terminate to a small stud. Pull that nut and wire brush the contact surfaces.
Also, pull the connector off the headlight bulb and be sure there is good contact there. The act of pulling them and reconnecting several times will burnish the contacts.
Do you have a voltage tester? Check the voltage at the bulb connector. It should be close to the voltage you read across the battery terminals.
The headlight door motor is not exactly speedy when functioning properly. This observation may be a red herring.
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