Lotus Elan

Curious headlight switch behaviour?

PostPost by: Doctor924 » Sun May 22, 2022 7:30 am

Hi everyone
I’ve posted elsewhere on this forum about ongoing trials of fitting what seems to be a 130 loom to a SE car, but have been making progress.
My current problem is as follows.

I’ve been trying to figure out the wiring for the headlights. Starting with the dipped circuit.
I have a light switch that combines the micro switches with the vacuum control.
Currently, if I twist the light switch slightly the sidelights come on
If I pull the knob out, the sidelights stay on but nothing else happens, no dipped beam.
Checking the wiring for the dipped beam relay, the switched supply is fine 12v live all the time, the switching supply takes its 12v feed from the live switched supply (blue/white) and seems to then use a switched earth to then trigger the relay to activate the headlights. So if I short the switching supply and earth the pin, the headlights activate and the relay closes.
The switched earth seems to be a black/red wire in the engine bay which I assume would have connected to a micro switch on the drivers side light pod. My car doesn’t have this switch there, with the micro switch on the light switch unit it seems. And indeed when I pull the light switch out two of the contacts on the lower light microswitch have continuity. So simple I thought. Just run a new cable to the black/red switched earth in the engine bay to the micro switch so that when I pull the light knob, the relay is triggered and the dipped beams come on….but nope.
If I have the sidelights on (or off) and pull the knob, the switching supply is not earthed to activate the relay and dipped beam. If I disconnect the black/red cable from the microswitch and earth it manually, the dipped lights come on. Anyone have any ideas about why when I connect then black/red and an earth to the microswitch, I don’t in fact earth the switching supply? It seems very odd to me.

Pics to flow btw!

Thanks
Ian
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PostPost by: billwill » Sun May 22, 2022 1:37 pm

The Vacuum pull 'switch' on my S3 coupe is totally independent of the electrics. Turning the lights on & main/dipped are dealt with by ELECTRIC switches separate from the vacuum valve.

One 3 position electric switch on the dashboard does OFF -> SIDELIGHTS -> Sidelights + MAIN. The column switch does DIPPED -> MAIN-beam.

Bringing the lamps up, with the dashboard switch OFF, used to make the main beam flash at about 2 second intervals (controlled by a microswitch somewhere that detected when the lamps were 'up.) but that circuitry was removed by Vegantune of Spalding back in 1983 during a refurb. As I think flashing headlights automatically had been deemed to be illegal in the UK.
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
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PostPost by: 10kph » Sun May 22, 2022 2:52 pm

The headlights on a post 1971 car work opposite to the earlier cars due to "failsafe " regulations and the operating switch is different
Earlier cars turned the lights on when the microswitch earth as the vacuum lifted the lights.
Later cars have the vacuum operated by a solenoid which pulled the lights down until activated by the light circuit which released the vacuum.
Possibly easier for you to use a Mazda headlight motor for operation rather than reversing the vacuum system
Tony
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PostPost by: Doctor924 » Sun May 22, 2022 2:59 pm

Yes thanks I was thinking of going electric on the headlights, but I might out of curiosity see if the vacuum system could be made to work once I get the engine started after it’s 40 year slumber.
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PostPost by: mbell » Sun May 22, 2022 3:23 pm

Late s130 cars have a different light switch. A simple toogle switch, off, side lights, headlights. A solenoid near the right corner of the radiator controls the vacuum for pods and power for the lights goes straight to the lights. There are no micro switches.

I think you really need to figure out what loom you have and assess if you can make it work or would be better getting the correct loom.

Have you a manual with the different wiring diagrams?
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: Doctor924 » Sun May 22, 2022 5:25 pm

Hi
Yes got the manuals and the loom does not correspond to any of them!
Ho hum…
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PostPost by: 10kph » Sun May 22, 2022 8:17 pm

Reading about your problem again I assume that you have 4 relays near the exhaust. One for sidelights,one dip and one mainbeam.. if that is the case then without the engine running to create a vacuum you will have to raise a headlamp pod with your hand to activate the microswitch which also may need the screw adjusting if in working order
Tony
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PostPost by: Doctor924 » Sun May 22, 2022 8:23 pm

HI

The car came stripped - all bar the engine was out. With the car in boxes really, I did find three old relays which I assume are those you are referring to? Headlights are up anyway as they 'failsafe' I understand.
The new loom has four relay connectors (the more modern box type) - main, dipped, rear screen, horn - in the cabin. I've wired up the first two and they work in a fashion OK (I just expected the microswitches on the lighting switch to work as I understood them but still think I'm missing something). I can see the connection for the vacuum hoses on the front of the boxed chassis section so I guess i'll follow the layout in the parts manual to see if it works at all. There were no microswitches near the pods nor have I found any in the spares (so far!).
Thanks
Ian
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PostPost by: 10kph » Sun May 22, 2022 9:01 pm

From what you now describe, the four fuses in the dash are not relays and so it is a 130 loom which does not have relays fitted as standard but two thermal fuses secured behind the dash near the light switch. This loom operates the lights directly with the round turn and pull switch and the vacuum solenoid to release the vacuum.
No microswith is needed and could be from an earlier car. Your wiring diagram is european 130.
Ps.. you have the simpler wiring loom compared to pre 71 models
Tony
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PostPost by: Doctor924 » Sun May 22, 2022 9:32 pm

Thanks and I’m glad is simpler!
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