Hey Guys - Read through alot of posts on similar issues, but out of the blue, my C3 headlights do not go up, nor are they illuminating (when in down position or when I've maunally raided them). It could have been at least 12 months since id tunred them on, one used to be a bit slower than the other, but definitely worked. All other lights (parkers, dash lights, tail lights and "lights on" indicator on dash) work.

I replaced the switch immediately, no change.

I don't understand why bot the electrical system or vacuum system would fail at the same time unless it was the switch (I assume, but can't 100% recal, but when the switch is pulled on, it should illumiate the lights even if theyre stuck down or partialy open??)

I started down the vacuum system using the fault finding quide on the forum and diabrams. I almost has myself conviced the relays were sticky, so I fitted new ones, nothing.

I "isolated" the vacuum system to just the headlights (unplugged / re-routed any lines that were to do with windscreen washers as my vacuum testing was loosing some there.

At this stage, the only part of the system not consitantly holidng pressure is the "green" side of the LH headlight actualtor diaphram (so maybe front rod seal not 100%). It will manual lift when I pump in vacuum, but doesnt hold pressure up. Red side (down) all good. But even if I isolate that side, the RH still wont come up off the switch / with car vacuum. I can make both open and close by pumping up green or red tube on actuator independantly, but can't make it go up by pinching white signal tube tube when car running.

Pulling my hair out....and idea's why both "systems" may be at fault at same time?!?!

 

First off, what year do you have?
Secondly, can you manually push up both lights from underneath such that they lock and stay open by themselves? When they're fully locked open, have you tried cycling the dimmer switch?
When you pull the headlight switch to the first detent, do your parking lights illuminate?

Lastly, what city are you near? There are several Aussies here on the forum that may be able to assist in person.

 

Hey Mate - In Cairns.
1973
I havn't "pushed" the lights open, but used a vauum pump on the green line to the actualtor, pumped them tpo the up position, then yes, they stay up and locked till I pump them back down on the red line.
Yes, when I pull on headlight switch to first detent and second, parker light up. All other lights work, tail lights, parkers, dash light, and "lights on indicator on dash"
No I havn't tried the dimmer switch when th lights are up (you mean the high / low beam dimmer / selector switch?
Cheers

 

Sounds good that the parking, tail lights, and dash all light with the switch - that seems a good omen for the switch.

Yes, by dimmer switch I mean the high/low beam selector on the floor. I'm wondering if the switch is on low beam but the high beams work – it's just that you haven't tested that yet. Here's a recent post on the C2 forum about testing the H/L switch where the problem is no low beams (pre-'77 C3s share the same design as the C2s):

 

Thanks, I'll try dimmer switch!

However, am I correct in saying / assuming the electrical problem with the lights not coming on is unrelated to them not coming up?

 

Yes! You have two separate problems. To power up the lights electrically:


You changed the light switch, as the hoses are on correctly?

After the electric part is fixed Use this vacuum troubleshooting guide:
http://www.corvette-101.com/vacuum.htm