vmsns007

Pull headlight switch - lights power up but doors wont open - have read they are vacuum operated.
Start tracing hoses and i find the one in the attached pic severed in half (the top hose connected to the multi port object). It runs to what almost looks like a washer fluid tank. Related to the door not opening ? If not - pointers ?
This is a 74.

Peterbuilt

Not sure where those hoses start from but they are connected to the windshield washer pump.

Here's a headlight troubleshooting guide;

http://www.corvette-101.com/vacuum.htm

Many times it's the seal (grommet) in the headlight actuator that goes bad, but it's best to check every component.

Tooch1

Don't be alarmed when you look for the headlight bypass switch that Alan shows above. On your 74 there is just the one black plastic pull-down switch mounted there. Starting in 73, there is no longer a vacuum operated wiper door on the cowl (that's what the **** and other switch are for on 68-72 cars). But the switch serves the exact same purpose. Use the vacuum hose diagram that Peterbuilt included.
When you pull your headlight switch to turn on your lights, does the headlight warning red light on the center guage console light up? It should! It serves as a safety warning letting you know they didn't pop up, and to use the bypass switch.
You definitely need to get a plastic vacuum hose union to get that severed windshield washer hose back together. Kit assortments are sold at all local auto part stores.
After you check all of the above, and all your hoses are free of leaks and attached correctly, and your headlights still don't pop up on their own without using the bypass switch then most likely you will need to replace your headlight switch. Not a fun job, but one almost every early C3 owner needs to do at one time or another.
If it is your switch, I'll be happy to help you through replacing it, as will many others here on the CF.
Hope this helps, let me know.

Regards,
Jim

vmsns007

Thanks for great pointers.
I have enough here to get started troubleshooting.
I know i can manually lift the headlight assemblies but is there a mechanical way to lock/unlock them in that position until i can properly fix issue but still be able to drive at night ? (Again the lamps come on but assembly won't pop up)

SwampeastMike

The headlight doors DO lock themselves into the "up" position but such won't happen by simply lifting them. Sorry that I can't supply photos now but if you watch the mechanism from underneath the car as someone else lifts the doors you'll see how the rod from the vacuum motor over-extends a touch to make a physical lock. If you disconnect both vacuum lines to the headlight vacuum motor it's quite easy to operate the mechanism as it is nicely spring loaded in both directions.

I suggest a purchase for you: A Mitee Vac (or similar) hand vacuum pump--they're inexpensive and you'll find them at any auto parts store.

Also, unless you are positive that the hoses in the system are quite new, get a complete new set of headlight vacuum hoses from Doc Rebuild. Trust me--old hoses that look and feel fine and test leak free when removed are most likely leaking at EVERY connection!

One last thing: The currently available vacuum motors and vacuum relays from any vendor are crap! From what I read here you can have original relays rebuilt for a reasonable price. If a relay tests bad be certain to investigate if it is an original and then send it out for repair or study about DIY. The original vacuum motors often leak from the front boot around the rod. You can get kits to make excellent repairs. Do your research about how to install them properly. Should your test show that you have a leaking diaphragm (the rear connection does not hold vacuum indefinitely) order a replacement and test before installation under the highest vacuum you can get from your hand pump. It should hold vacuum indefinitely--think overnight it should still be holding 15" or more of vacuum after pumping down to 25" vacuum. Test REPEATEDLY over a few days before you install!!!

7t9l82

You can use a vacuum cleaner with an adapter but take it easy.

rworley6641

Just a thought. You could consider converting your vacuum system to electrical motors that lift and close. The electrical system is an easy install, is extremely reliable and runs about $450.00. Completely eliminates all the vacuum guessing.

vmsns007

Interesting. Pointer to a product or existing thread ?

rworley6641

If your a do it yourself guy, look at "Vacuum to Electric "NEW WAY", here on this forum. If you want a kit checkout YouTube, Corvette C3 electric headlight motors or ebay, same search. Or email me at rworley6641@yahoo.com or call me direct 717-383-8154 for more avenues to attain a electrical motors conversion to open and close the headlight buckets. My name is Rich. Good luck with your endeavor either way.

Richard454

I have a PDF put together on how to do it and what's needed-

Just shoot me and email - richard454@comcast.net

Here's the thread-
https://www.corvetteforum.com/forums...c-new-way.html


Mine-


And a fellow forum member-