Headlight rotator switch

[Michael G.]

As you guys may remember, a few weeks ago I had a problem with the headlight rotator switch failing on my red '65. Finally found a used original switch and am waiting for it to arrive. we'll see if that fixes it.

Meanwhile, as I completed the PV pre-check for my other (black) '65, guess what didn't work? Right, both headlights won't turn, either way. So, I removed the switch and tested it, its fine. I then tested the power coming from the connector's red wire, it's fine. Then I tested both sides of the circuit breaker. Both are at battery voltage. My guess, at this point, is that I should sell the car...

Seriously, what's next? I'm thinking that I need to apply a fused 12V to each of the rotator wires (not the hot one), to see if I have a short somewhere in one of those. Given that I'm not an electrical engineer, is there a better way to look for the short?

By the way, they both worked last time I drove it at night.

Thanks,

[Timothy B.]

Re: Headlihght rotator switch

Michael,

My next point of elimination would be a bad ground at the headlight motor or at the front light wire harness ground to core support. Look for that wire on the drivers side where the harness crosses the support.

[Larry M.]

Re: Headlihght rotator switch

The wires to the headlight motors go thru the firewall bulkhead connector. It may be pulled apart a bit causing an "open" circuit to the motors. Check it out.

My own headlight motor issues were caused by the bulkhead head connector separating. Locked them back together and no more issues.

Larry

[Richard M.]

Re: Headlihght rotator switch

Mike, Likely a "Open" versus a "Short". If it was a Short the Circuit Breaker would remain open and be clicking every few seconds.

Are you rolling the motors with engine running or not? If not, try it with engine running that may be a indicator where to proceed.

How did you test the Dash Roll-Up/Dn switch? It's possible it may test good with a simple meter, but high current passes through it during operation so any carbon buildup could prevent motor operation.

The grounds for both motors are sourced from the radiator support terminal as mentioned. IIRC, at the horn relay mount screw from the forward harness. If that ground is open, then your front park lamps and headlights would not illuminate either. Are those working?

The actual grounds for each motor are attached to the header bracket and into the motor cases. Ensure you have a clean connection on each, with a star washer between the Black wire terminals and bracket to case. Those small hex head machine screws are a short length. If too long they can pierce the internal field coil of the motor. This would be a short when trying to operate them.

If the Roll-Up/Dn switch is good and has power(red), the next test would be at the motors at their connectors. But first check the outer Bulkhead connector in the engine bay at the firewall. The Green and Blk/Yellow outputs from the dash switch pass through that connector, so check for corrosion or open contacts there. Seems unlikely both would be open, unless there is heavy corrosion inside the connector or simply misconnected due to loose or a broken plastic tab, etc.

Rich
edit... Larry got it too as I was typing and trying to make a diagram....

[Michael G.]

Re: Headlihght rotator switch

Michael,

My next point of elimination would be a bad ground at the headlight motor or at the front light wire harness ground to core support. Look for that wire on the drivers side where the harness crosses the support.

OK, so the rarest screw in captivity is the "Hi-Hat" tapping screw that holds on the 'S' tube. This, for some odd reason is also the screw that attaches the headlight ground to the core support. Ignoring the fact that I just dropped the screw to the most inaccessible location in North America, why in the heck did someone use a phosphate coated screw for this high current ground? Jeeeeeze

[Michael G.]

[Michael G.]

[Michael G.]

Re: Headlight rotator switch

I replaced the ground screw with a zinc plated one and a better star washer, then took the switch out. I then replaced the switch with a toggle between the "up" wire and the feed. Zooooom, even with the engine shut off, the headlights rotated faster than ever before, ....

Now I'm wondering if the switch would work again, now that I've the improved current flow through the ground...

Thanks all,

[Michael G.]

Re: Headlight rotator switch

I disassembled the switch and it looks fine. I'm going to clean the contacts, put it back together, and try it out

[Michael G.]

Re: Headlight rotator switch

Perfect!!! All cleaned and back together, works great. Wasn't much carbon on the contacts. Gotta believe it was the crumby ground. Probably enough flow to ground for the parking lights, but not for the two motors. Using phosphate coated bolts and screws for grounding has long been a no-no at GM, for just this reason. I might add a wire to the frame, so its grounded to something other that sheet metal too.

Thanks everyone!

[Richard M.]

Re: Headlight rotator switch

Mike, Good troubleshooting technique and diagnosis.

Yes you may have had 2 faults and when combined caused your problem. As you know it doesn't take much to create high resistance in those switch contacts, particularly originals.

Well Done.
Rich

[Michael G.]

Re: Headlight rotator switch

Thanks Rich.

As an aside, what I noticed during this investigation is the the repro switch that I took out of my other 65 has spring contacts that are extremely difficult to bend compared to the originals. No wonder that the plastic of the rocker on the repro had been shaved off by contact with them…

One thing I learned in all my trouble-shooting days in GM plants is that usually problems don’t become serious unless their are at least two of them happening simultaneously contributing to the issue