CrossedUp

I've completely gone through my '69 headlight door mechanisms; new actuators, plastic bearings, springs, warning switches, cotter pins etc. Installed, positioned and shimmed the frames to align the doors with the body. Adjusted the up and down stops as per the AIM. Now I'm trying to adjust the clevis rod length.

The problem is when the doors are in the closed position. The down stop is in contact with the adjustment bolt as it should be, the doors are flush with the body and everything is fine. This is with atmospheric pressure on both sides of the actuator. If I pull a vacuum on the back port of the actuator (as it would be when the headlight switch is off) the doors go down another ~1/4" or so. Is this abnormal or expected behavior? So far I haven't been able to figure out the cause. I've done a few forum searches but haven't been able to find a thread that deals with this issue.

Thanks,
-Doug

Alan 71

Hi Doug,
WOW!!!!

Shouldn't the 'down-stop' prevent the door from closing any further regardless of the vacuum present in the 'close' side of the actuator?

Regards,
Alan

CrossedUp

Yes Alan, one would think so but, when the door is down without vacuum applied, the down-stop bolt pinches a piece of paper.

Alan 71

Hi CU,
Doesn't the top surface of the head of the adjusting bolt interface with the notch cut into the elbow.
Isn't that a metal to metal contact?
Am I missing something?
Regards,
Alan

CrossedUp

It does, it is, and no Alan you aren't missing anything. Pictured below is without vacuum applied. It seems that the whole mechanism flexes a little just prior to the diaphragm bottoming out.

Alan 71

Hi CU,
I notice the nut on the adjusting screw!?!
It's not shown in the AIM and I'm pretty certain there weren't any on the adjusters on my 71 headlights.
Is there ANY chance that's part of the cause for what you're seeing?
Regards,
Alan

Dave J

Am I correct in that you have not adjusted the clevis length yet? If so you must do so before so you will not have any more travel in the actuator rod. The correct order of adjustment is; "W" bracket, then Clevis, and finally the adjustment bolts.

The correct procedure can be found here: (Reference; 1970 Chevrolet Chassis Service Manual; Electrical - Body & Chassis - Section 12-3)

CrossedUp

Right, I added the nuts to lock the adjusting screws in place. They spun a little too freely in my judgement. They are well out of the way and don't seem to have an affect on anything. I'll remove one and retest.

Thanks Dave. I tried the AIM method (1/2 turn past touch condition with lamps up) but the issue persists. I'll try readjusting using the actuator rod travel limit as a reference and see if that helps.