Headlight help needed

[althelodger]

1978 Silver Anniversary:
Just to put things into perspective, I bought the car with one headlight out but the seller sold it with a conversion kit from sealed beam to conventional H4 and H1 bulbs.

When I checked the lights, there was indeed one light out when on main beam(only 3 lights on)

It appears that the outer lights are dipped beam and the inner ones are main beam-is this correct?

I’ve replaced the outer sealed beams and these are now running H4 bulbs, so far so good.

With low beam on, I have the 2 outer lights on.

When I switch to main beam, I have a light out but it’s the drivers side low beam light which is now out, which was on when on low beam!

It wasn’t until I videoed the lights operating that I realised this was happening!

Am I looking at a faulty light switch or could it be a bad earth?

I’m hoping it’s not a fault in the wiring somewhere as I’m not good with wiring-I can change bits and hopefully find earth points but that’s about it!


Many thanks

PS, I wanted to upload the above video directly into this post but I could only add photos not videos, hence the YouTube link

 

[Roscobbc]

Glass' bodied Vettes, separate chassis and electrical gremlins do go hand in hand unfortunately. Your gremlin could well be an earthing issue - from my experience the earing issue can sometimes be in a totally different location bizzarely - might be worth checking earthing to rearlights and headlamp mechanism to frame.

 

[althelodger]

Thanks for the suggestions. Funnily enough I do fear something a bit deeper as I was getting flashed by other cars the other night from behind and in the opposite direction. I got home and checked all the lights and they were all on. I was wondering if the lights could be going off and on as I was driving along. I think I may well need to get the missus out in her car to both follow me and lead me and see what she can see.
I did a rough alignment check the other day and they are low if anything.

 

[Chuffer]

Thanks for the suggestions. Funnily enough I do fear something a bit deeper as I was getting flashed by other cars the other night from behind and in the opposite direction. I got home and checked all the lights and they were all on. I was wondering if the lights could be going off and on as I was driving along. I think I may well need to get the missus out in her car to both follow me and lead me and see what she can see.
I did a rough alignment check the other day and they are low if anything.

Are you now saying that all your lights may going on and off whilst driving ? That would account for other drivers flashing you . The C3 head light switch has a thermal cut out built in to protect the circuit as perversely the lighting circuit is not protected by a fuse . The thermal cut out will switch off the head lights when it get too hot with current draw which can often happen when running on main and dipped beam together , especially if non standard lamps are fitted . When the thermal cut out cools down , the contacts remake the circuit and the lights come on . The on / off sequence can happen with scaring frequency .

 

[CaptainK]

Could try videoing the rear of your car too when you go to dipped beam on, then to main beam on etc to see if your rear lights are doing anything weird.

Possibly try disconnecting each light front and rear and repeat the process to see if anything different happens? With the aim to possibly find a culprit.

On a different note, your vacuum headlights are not working correctly by going down one at a time. Probably a vacuum issue - broken hose or some such - or possibly a sticking headlight mechanism. I had a sticking headlight mechanism and made it run slow.

Oh and congrats on the H1 and H4 headlight upgrade. I did similar, but put LED bulbs into the car too, with the thinking that they use less power so shouldn't tax the old wiring too much.

 

[johng]

When you switch to high beam you are using a different filament in the outer lights. There are 2 filaments in the dipped beam bulb, a high beam and a low beam, see the wiring diagram below. Both filaments use the same earth, so it won't be an earth problem. Either you have a broken high beam filament or a bad connection where the cable plugs into the bulb. You are getting power to the drivers side inner light, so it can't be a switch problem. For some reason the wiring diagram suggests that the dual beam light is on the inside, it isn't on my 78, it's on the outside like yours.

 

[Roscobbc]

Might be worthwhile checking the advertised current draw of the H4 bulbs doesn't hugely exceed the stock bulbs.
Presumably main beam is wired so that the two main beam only and the main beam of the dual filament bulbs are all operating........and that someone hasn't wired dip beam (on the dual filament) to also come on for more light?

 

[johng]

........and that someone hasn't wired dip beam (on the dual filament) to also come on for more light?

If they had then all 6 filaments would come on regardless of whether you switched to main beam or dipped beam.

When I fitted H4 and H1 bulbs I did get the problem of the headlamp switch circuit breaker cutting out, with the consequence of suddenly having no light at all on a dark country road. That might just have been due to my aging switch cutting out at a lower load than intended, but a relay fixed the problem quite simply.

 

[teamzr1]

Stock GM outside lighting as of 1979 C3
But if using 3rd party lighting system may have added relays and ballast wiring

 

[althelodger]

Just videoed from the rear while going through the lighting from side lights to main beam and back again with not a sign of anything untoward at the rear lights.
Still need to get it out for a drive to see what’s happening!

 

[CaptainK]

Have you tried swapping the headlight bulbs from left to right to see if it still does it? I mean you know one of the bulbs works fine, just to rule out any bulb issue when going from low to high beam.

 

[althelodger]

Thanks CaptainK, I'll give that a go and post my findings