One of my Gen 1 headlight motors has a twitch which eventually drains the battery. It opens normally and closes normally but then occasionally does a little quarter rotation twitch. I don't hear any relay or internal switch clicks, & when I took it apart, everything appeared to be ok & the switches were functioning properly. So... if anyone has an idea of what's going on there, I'm all ears!
From what I've heard, the most common reason for that to happen is the rubber seal at the top of the motor housing (just below the knob) is above the casing rather than in the groove it was intended to be. Having said that, I have the same problem, but mine is in the right place. I think my limit switch might be shot.
It has to hit the limit switch hard in order to shut off properly, at least on mine. I had a similar problem when I installed the rubber bumpers that came with the Dickman kit. The "fix" in my case was to fill the gear with JB Weld, as suggested by buddycraigg some time back. It would seem that a soft stop is desirable, but the design just doesn't cooperate. Obviously some motors are worse than others, I'm sure the bumpers work for most people. That said, the above motor still doesn't work 100% so there may be other issues. On rare occasions it fails to open unless I give it a hand start.
It doesn't actually solve the problem, but I think if you cut the white wire at the headlight switch you can keep it from running the battery down. You install a switch and turn it on just to lower the lights. You could even use a momentary switch, a push button. Without the white wire the headlights don't go down, and presumably, don't continue trying to go down when they already are.
Some of the black rubber bump stops supplied with rebuild kits can cause the ticking problem. Like amos said, the motor has to come to a pretty abrupt halt in order to fully disengage the points. Soft bump stops will keep the points close and as they compress a little more, they will make contact again. If you replace them with something much harder you can put too much stress on the plastic gear and strip the teeth or break the fingers off the drive plate.
I have experimented with a number of materials including threaded rod, hex nuts, and wood dowels and I found that within a month the teeth of new gears were starting to show signs of sheering. Before taking the motors apart again, look at the brushes to be sure they are both still attached. Sometimes when reinstalling the limiter switch assembly, the brushes catch on the motor and one will break off. The motor can still run, but doesn't have enough speed or torque to fully complete its cycle.
If you find no other cause, I sell a set of bump stops that has solved the problem for a goodly number of people. They're $5 for a set of 4 or $8 for a set of 8.
I'm using a switch now to turn the power off. About 25 years ago I installed a set of driving lights in case the headlights didn't go up. After 3 sets of driving lights deteriorated I gave up on that idea. I left the switch in place near the ashtrays and the hot wire in the front and have used it several times to power the down cycle until the grinding started then turned it off. After gear replacement, I just coil the wire up for the next time.
I seem to recall not using bumpers on at least one occasion - I think the drive claw either fit closely to the gear webs or would just whack the webs & everything worked ok.
The Gen 2 unit's drivers on my '88 are hard, but still had to be replaced because they crumbled into little pieces.
Without bump stops, the fingers on the drive plate have some slack when starting their up or down travel. They make a pretty hard stop against the gear ribs at the end of travel. The material I use for bump stops is compatible with the lubricant I use and has resolved the ticking issue in all but one R&D case and in all end user cases. I wouldn't expect them to crumble for many many years, if ever.