1973 Slow Headlamps

[Timothy K.]

Hello All-

Need a little help/direction. Just for drill, I activated my headlamps on my '73 just to make sure everything was working properly and to my surprise, the headlamps rose very slowly, especially the left one which came a 1/3 of the way up, stopped, then rose to the full upright position. I very seldom use the headlamps and they have always popped to 'life' in the 30 years I've had the '73. I tried it several times with the same result. I re-lubed the various pivot points and checked the hoses but still the same result. I've seen many articles on this but really never paid much attention since the headlamp operation on the car was always stellar...until now. Unfortunately I've just moved and all my shop manuals/information are in storage miles from here so I'm flying blind.

If someone could provide me a good diagnosis 'tree' on this, I'd really appreciate it. I just don't want to start throwing a bunch of parts at this.

Many thanks,
Tim

[Joe L.]

Re: 1973 Slow Headlamps

Hello All-

Need a little help/direction. Just for drill, I activated my headlamps on my '73 just to make sure everything was working properly and to my surprise, the headlamps rose very slowly, especially the left one which came a 1/3 of the way up, stopped, then rose to the full upright position. I very seldom use the headlamps and they have always popped to 'life' in the 30 years I've had the '73. I tried it several times with the same result. I re-lubed the various pivot points and checked the hoses but still the same result. I've seen many articles on this but really never paid much attention since the headlamp operation on the car was always stellar...until now. Unfortunately I've just moved and all my shop manuals/information are in storage miles from here so I'm flying blind.

If someone could provide me a good diagnosis 'tree' on this, I'd really appreciate it. I just don't want to start throwing a bunch of parts at this.

Many thanks,
Tim

Tim------

I'd say there is a vacuum leak somewhere in the system. Most likely, it involves the shaft seal on the headlight vacuum actuators although the fact that both of your headlights are affected makes me a little suspicious that it might be something else in the system. In any event, you probably don't need to replace the actuators as shaft seals, never available separately from GM, are available in the Corvette aftermarket and are relatively easy to install.

[Tom R.]

Re: 1973 Slow Headlamps

Tim

I'm attaching two troubleshooting guides that compliment one another. I've used both of these to troubleshoot the same problem you describe and after replacing the relays, eventually had the vacuum actuators rebuilt. Now they "pop" as you describe. The actuators have diaphragms in them that eventually deteroriate. One of our members (Bob Demmel) did the work and returned the worn diaphragms that leak vacuum. He advertises in the Driveline. Hope this helps.

HeadlightVacuumTutorial.pdf
Vacuum System Troubleshooting.pdf

[Timothy K.]

Re: 1973 Slow Headlamps

Tom & Joe-

Thanks for the insight and help. I was always so happy that my headlamps were so 'crisp' in their operation but all good things must come to an end so this will be a good late Fall/Winter project.

Thanks again,
Tim