Headlight motor only runs one way????

[James W.]

I finished rebuilding a pair of 1967 Corvette headlight motors for a friend and went out to test them tonight. I took the right side motor out of my '65 and installed the newly rebuilt '67 "right" side headlight motor. It worked perfectly in both directions several times. I removed the rebuilt '67 right side headlight motor and reinstalled my '65 right side motor. I proceeded to do the same on the left side but the newly rebuilt "left" side '67 headlight motor would not open the left side headlight. I manually opened the left side until it was fully open and hit the switch and it closed by itself but would not reopen.

I went completely through both of the headlight motor assemblies and cleaned them. I also cleaned and replaced the driven gears in both gear assemblies and cleaned and regreased everything. I've done at least 12 pair of these motors and never have had this problem. I can't say for sure if the motor worked in both directions before they were given to me by the owner. I will be asking him this question tomorrow.

What could be wrong with the left side headlight motor?

Any help would be greatly appreciated.


Thanks,

James West

[Richard M.]

Re: Headlight motor only runs one way????

James,

I'd do this......with the motor out and on the bench I'd test in both directions by connecting to a battery with jumpers. Ground(-) the case, then +12v on each terminal of the connector to verify the motor runs in both directions. I suspect you will find the motor is bad since you verified the switch and wiring using your own motors from the 65. Another clue to me is you weren't sure if it ran both ways before the gearbox rebuild.

These motors have 2 oppositely wound field windings to reverse the armature spinning direction, each powered by one of the 2 +feed terminals in the round connector, unlike basic 2 terminal motors which reverse direction simply by switching polarity between the + & - terminals.

I have opened these up before and typically found a broken connection inside. If you're up to it you may find that's the problem. It's a bit tricky getting them back together because you have to hold the commutator brushes apart to get the armature back in. I use a stiff wire, crisscrossed to make a spring to hold the brushes apart, carefully getting the armature relocated.

edit: Also check the thermal overload contacts. A simple cleaning may solve it if it's that.

If you open it up and see no problems, it may be a bad winding(open circuit) in one of the 2 fields. In that case in my experience the motor is not repairable.

Rich