Some info on the your headlight system and why it does not always work right
Thru the years I have been asked like thousands of times basically the same question: My headlight lift system does not work the way they should. How do I fix them?
The simple answer is there is no simple answer. If one or both headlights do not come up when turned on but might if you spin the knob slightly or does not go down for that same reason there is generally no single thing you can fix or replace to make them work like new again.
The other common problem is the armatures twitch and drain the battery down to completely dead.
The biggest single problem IMO is low voltage to the armatures. Thru the years every connection (especially the grounds) get slightly corroded which reduces the flow of electricity to the armatures in the headlight motors. This is a common problem on any older car. Start at the battery and work thru the electrical system cleaning everything you can and regreasing everything. Even the headlight switch can be opened up, cleaned, regreased and put back together.
The headlight motor has to have enough strength (inertia) to fully open the contacts when they get to the full up and full down position.
The relays on the headlight buckets are low cost and still available. The plugs may be degraded. I offer a kit to replace the original relays and the plugs. You can replace them. I also have a reproduction isolation relay the eliminates the plug insuring 100% perfect connections.
If you have not opened the headlight motors you should do that. In most cases you will want to replace the gear and bumpers right away. When new these headlight motors had grease in them. Over time that grease dries up and turns into a clay like material. Clean everything and regrease it. Hi temp grease is the best grease because it is slow to dry up.
There is one wire on the brush/contact assembly that can be soldered to the arm making a better connection. If a brush has fallen off or is worn to nothing I have new brushes and the correct glue to glue them to the arms.
Clean the battery cables (both ends). Make sure the small ground wire is intact and working well. Clean the wires to the positive junction block next to the battery.
I've seen many times where a crimped on terminal end is corroded under the crimp. The only fix is to cut it off and install a new crimped on eyelet. You may have to sand the wires as sometimes the corrosion makes it way back up under the plastic insulation. It is best to then solder the crimped end on to the wire.
Glass bulb bi-metal switch mistery solved:
Everyone thru the years has wondered why that bimetal switch bulb is in these headlight motors. A few years ago someone called me and told me their bi-metal switch failed shut and the headlight motor got very hot and you could smell it. So I now finally knew why they put in the bi-metal switch.:
If the contact does not open and stay open the armature stays energized and gets hot. The bimetal switch will keep opening and closing until the battery is 100% dead. Why? Becuse there is a chance the armature might get so hot it could cause a fire. Pulsing it keeps the headlight motor cooler.