Headlights stopped… then came back

[Brinyan]

Driving home just now, headlights on all the way, full beam for about half of the 40 minute journey. Mile or 2 from home, slight flicker of the lights, then they’re off - very dark!
Used my indicator for limited light until I could pull in off the road. Turned light switch off, phoned home to tell my wife she was right & I should have taken another car. Tried switch again & lights came back on.
What may have happened - overheated something? Wouldn’t be a fuse, as they came back on. It’s a 1973 Scimitar GTE.

[alfaspecial]

Brinyan said:

Driving home just now, headlights on all the way, full beam for about half of the 40 minute journey. Mile or 2 from home, slight flicker of the lights, then they’re off - very dark!
Used my indicator for limited light until I could pull in off the road. Turned light switch off, phoned home to tell my wife she was right & I should have taken another car. Tried switch again & lights came back on.
What may have happened - overheated something? Wouldn’t be a fuse, as they came back on. It’s a 1973 Scimitar GTE.

Here's your answer: It’s a 1973 Scimitar GTE.



Scimitars have a fibreglass body and earthing can be a problem. I'd be inclined to start by 'fiddling' with every connector to the light unit(s) and to the earth chassis connectors to make sure the earth wire/connection are not damaged.
By fiddling I mean remove the connector, clean both spades with emery cloth and reassemble giving a quick squirt of WD40 or similar to keep future water ingress / corrosion at bay.
And do a similar inspection / clean of the fuse box terminals.
If this doesn't do the trick it could, of course, be a dodgy light switch. And maybe, when you turned the lights on you didn't quite make a complete contact so the poles of the light switch didn't quite make a permanent contact. Being 'just' a little more forceful (turning the switch and then giving it a slight secondary twist might help).

Edited by alfaspecial on Friday 10th February 07:19

[Jordie Barretts sock]

Bad earth for sure.

Happened one night on my mate's Suzuki GT125 two of us on it. He'd fitted a halogen light unit from a car. Which was great until the earth came completely detached as we approached a sharp right on a country road. Luckily there was a field straight ahead and we ended up 100m into it.

Edited by Jordie Barretts sock on Friday 10th February 08:00

[jr6yam]

Years ago I had the same thing happen in my Vauxhall Magnum. There was a circuit breaker in the wiring loom, shorted it out and the problem never happened again!

[Mark A S]

My first car, Mk 1 Escort 1300 sport used to do this occasionally, normally when pressing on over the back roads! It was the bullet fuses, wiggle them and the lights came back on. Removed them all, cleaned up the terminals, some WD and it never happened again.

I have no idea if your car has these types of fuses, but if so, that's where i would look first.

[steveo3002]

id be looking at the switch , do these have a relay as well or no

id guess it got hot then cooled after you pulled over

if it has relays check the pins are clean , pop off the lids and look for corrosion , and cleaning the earths up is never a bad idea

[Turbobanana]

I had the same problem in my Triumph GT6 on the way back from buying it in September (the day the drought broke and it chucked it down all the way home). Got to within a mile of home and it all went dark.

Turns out it just needed the fuse box fiddling with: there's only 3 fuses in a GT6 and they were all loose.

[droopsnoot]

jr6yam said:

Years ago I had the same thing happen in my Vauxhall Magnum. There was a circuit breaker in the wiring loom, shorted it out and the problem never happened again!

HCs have a bimetallic strip to protect the lighting circuit, rather than a fuse. The idea is that if it overheats, just give it a few minutes and it'll cool down and the lights will come back.

One caught me out too, when I was unfamiliar with these things and had wired my lovely spotlights directly into the main beam circuit - and of course those "few minutes" are always on a nice twisty bit of road that becomes unfamiliar as soon as it's plunged into darkness.

[Cliftonite]

This was a feature of new MkI Ford Mondeos. Until the recall work had been undertaken.

Happened to me more than once. The virtually never-used front fog lights then came in handy.

[OutInTheShed]

Jordie Barretts sock said:

Bad earth for sure.

....

Edited by Jordie Barretts sock on Friday 10th February 08:00

On a plastic car?

The earth or 'return' wiring is unlikely to be common to hi and lo beam on both sides of the car.

If it all cut out together, look at the common part of the circuit.
Are there relays involved?

[Scotty2]

I had that issue with a Mini Clubman Estate. It was the switch for me as there were no relays.
I think SE5s have a rocker switch but SE6s had the same switch as the Mini Clubman.

[spoodler]

Sometimes with old cars, especially those that don't get used a lot, it's as simple as switching the switch on and off several times. The contacts can get a little fuzzy...

[Hol]

Mark A S said:

My first car, Mk 1 Escort 1300 sport used to do this occasionally, normally when pressing on over the back roads! It was the bullet fuses, wiggle them and the lights came back on. Removed them all, cleaned up the terminals, some WD and it never happened again.

I have no idea if your car has these types of fuses, but if so, that's where i would look first.

I was going to say the same thing, if it’s just the one circuit affected.
Those bullet fuses were so bad back in the day that many people used to stick a blob of solder on the end to stop them wobbling.

As I recall, the scimitar uses a lot of Capri parts, so it’s a likely cause.

As someone renovating a classic ford, I have to say I am surprised nobody is yet making direct fit replacements with blade fuses.

I do know someone who has a couple of Scimitars and possibly some spares squirrelled away, if the fuse box itself is toast?
No guarantees though, but I can ask.

Edited by Hol on Friday 10th February 10:54

[LuS1fer]

I had a 1981 Mustang and when I put it on high beam, it lasted a few minutes then plunged me into darkness.

I think that it was the headlight switch which had a bi-metallic cut-out, like an iron, to stop it over heating.

[Brinyan]

Thanks all. First check will be the fuses & clean them up, if needed. It’s a rocker light switch & haven’t had this issue before & have driven in the dark (with lights on!) many times over the past year, since I bought the car. Will look over the weekend. Cheers

[Jordie Barretts sock]

OutInTheShed said:

Jordie Barretts sock said:

Bad earth for sure.

....

Edited by Jordie Barretts sock on Friday 10th February 08:00

On a plastic car?

The earth or 'return' wiring is unlikely to be common to hi and lo beam on both sides of the car.

If it all cut out together, look at the common part of the circuit.
Are there relays involved?

The earth point isn't plastic is it Mr Pedantic? And if like my 'plastic' Chimaera it has H4 bulbs, then yes, the earth will be common for both low and high beam.

[spoodler]

Brinyan said:

Thanks all. First check will be the fuses & clean them up, if needed. It’s a rocker light switch & haven’t had this issue before & have driven in the dark (with lights on!) many times over the past year, since I bought the car. Will look over the weekend. Cheers

Nice to hear you're using it - loads of problems on old cars come from lack of use...
Those rocker switches don't usually play up, but I've a pull out and twist switch on one of mine and it's really temperamental... nothing compared to the expensive custom switch in my van, that was installed by simply wrapping some tape around the connections as both sides were male connectors and whoever "fitted" it couldn't be arsed with a couple of crimps... Made for an exciting drive home when the lights went out and the cab filled with smoke!

[Brinyan]

Thanks all. First check will be the fuses & clean them up, if needed. It’s a rocker light switch & haven’t had this issue before & have driven in the dark (with lights on!) many times over the past year, since I bought the car. Will look over the weekend. Cheers

[paintman]

Best couple of tools I had for my Scimitar - a 1970 SE5 - were long lengths of wire with a crocodile clip at each end.

Had the sudden 'disappearance of lights' on a Hillman Imp & that was a worn main on/off switch.

And the same with my Range Rover Classic which on both occasions were the dip/main switch contacts melting the plastic.
An issue with that particular switch & known on other cars that use the same one. Cured by fitting a new one but using it to switch relays instead of passing the main current through the switch.

[Lotus 50]

Are there any thermal cut outs in the headlamp circuits as others have mentioned above? They can start to go out of spec over time and cut out too easily or, if you’ve fitted brighter headlamps/sealed beam units the current draw can make them overheat and cut out. If there was a click when they cut out and another before they started working again it’s likely that this is the case.

They have these on Elans of similar vintage and they’re difficult/impossible to source. The best solution is to adapt the headlamp circuits so that the switch works via a relay reducing the load through the thermal cut out and putting fuses in the headlamp feeds for safety

Edited by Lotus 50 on Saturday 11th February 19:22

Edited by Lotus 50 on Saturday 11th February 19:24