MosportGreen66

Hi Guys,

I've been working on my 78 vette, trying to get a few kinks out.

The headlight buckets will not go up or down. I started by tracing all the vacuum lines. They are all hooked up and hooked up correctly. Then I replaced the headlight switch with a new one. Still not luck.

What else can I double check? The vacuum relays in front of the hood were recently replaced as well. They look new.

What am I missing here?

Thanks,
Dave

Iceaxe

Check the vacuum relays. Most of the replacement relays are faulty from the factory or will fail soon after installation. Don't assume any new vacuum part is good, always check them before installation to avoid additional headaches. Ask me how I know this.

And go buy a mighty vac now so you can test individual components. It's really easy to do and anyone that owns a C3 will end up buying one eventually so might as well buy one now and get ahead of the curve.

hunt4cleanair

I agree with Iceaxe

Next is testing the actuators...in addition to the seals, they have an internal diaphragm that deteriorates and affects performance.

I went through this cycle with my 78 and after testing the entire system, concluded the actuators needed rebuilding. They were installed two years ago. Drove the 78 yesterday and headlights "pop" like they were new!

bj1k

You can buy a vacuum tester at Harbor Freight . They are cheap and work well for this purpose.

Iceaxe

There are two types of C3 owners in the world... those that own a vacuum tester and those that will own a vacuum tester.

:-)

Dave J

Post of the Day!

MosportGreen66

Thanks guys. I appreciate the insights into the relays and actuators. I'll also definitely get a mighty vac.

Being that I have limited experience in these vac systems how do you go about testing the actuators and relays? Or even the full system? What kind of vac should they be putting out? Is there a more logical starting place than the relays and actuators?

Thanks,
Dave

hunt4cleanair

Do a search on troubleshooting headlamps. One of our members put together an excellent troubleshooting guide that takes one through each component and how to test it. This is what I used...it works!

It use to be tagged at the top or whatever they call it but I think the moderators lost focus...but then it could be there!

sierra 43

Hope you have better luck with this than I have had. My 74's lights worked great for about 4 months. Then the driver's one wouldn't close all the way. I adjusted, fiddled, tracked all the vacuum lines. Everything was ok. I did find that a previous owner used an angled "T" fitting to bypass the tank. I did away with the "T" , put the lines back to the tank and I had functioning lights. Last evening I was coming home around dusk, switched them on and nothing, other than the lights came on. Not up, just on. After a few minutes the passenger side came up, SLOWLY. Drivers side not so much. Then the car started run kind of crappy. Shut the lights off and it still ran rough. I think there is a vacuum leak that I just haven't found yet.

Dave J

Good place to start

http://repairs.willcoxcorvette.com/category/headlamp/