Lotus Elan

Main Beam / Dip Switch

PostPost by: gav » Sat Oct 26, 2019 9:07 am

Hi all

Been messing around with electric headlight lifters and decided to switch them using the supply to the dip switch so that when I switch on the main beam it lifts the lights at the same time. I have proven this principle and can control main and dip from the stalk.

My headlight flash units have never worked properly (the ones where you lift the lights using the vac switch and the lights flash as soon as the micro switches release) but that doesn't really bother me.

What does bother me is that I can't flash the headlights when they are on from the stalk. I can switch between main and full beam but the flasher action turns the lights off completely. I suspect that this is controlled by the 4th (brown) wire on the switch and that because the flash isn't working, this might be stopping the headlight flash on the stalk.

Two questions at this stage:-
1) what is the main dip lever supposed to do and in which circumstance
2) How do I get control of the flash from the stalk rather than the micro switches (ideally without harming the wiring loom)

Many thanks
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PostPost by: billwill » Sat Oct 26, 2019 2:16 pm

That's a risky procedure unless you reorganise the headlight relays circuits; the actuator will still be under power when the bulbs come on.

As supplied the full current fot the bulbs runs through the stalk switch which (In my opinion) was never intended to carry heavy current and putting your lifter actuator through there too will significantly increase that current making it likely that the stalk switch will burn out.

On the existing circuits the relay is used only as a safety precaution, to break the heavy current when the pods are down, they do not do the sensible thing of reducing the current through the stalk switch.

You would need (I suggest) to rearrange the relays circuits so that the stalk switch operates the coils of the relays which then turn the heavy currents on.
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PostPost by: gav » Sat Oct 26, 2019 3:05 pm

Thanks Bill - that's really helpful.

I need to think further on my approach.

The supply to the dip switch is intended to activate a switching relay that triggers a separate power supply to the light motors - the power for the lifting motor coming from a different circuit.

Does that alleviate the concern somewhat?

Thanks
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PostPost by: David1953 » Sat Oct 26, 2019 5:37 pm

My original dip switch did not have a flash option, just 3 wires.
But a recently bought replacement has the extra brown wire, and if this is joined to the the other brown supply cable then it does work as a flash switch.

I agree much better not to put too much current through this switch, but a dip relay and a main beam relay should be easy enough to add.

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PostPost by: lotusS2guy » Sat Oct 26, 2019 6:54 pm

Painless Performance sells a kit that adds relays and fuses to both high and low beams. it is prewired so that only relay current goes through the headlight and dip switches. I've used it on my Elan and my wife's 280ZX and it does the job.

https://www.summitracing.com/parts/prf-30815
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PostPost by: billwill » Sat Oct 26, 2019 9:36 pm

gav wrote:Thanks Bill - that's really helpful.

I need to think further on my approach.

The supply to the dip switch is intended to activate a switching relay that triggers a separate power supply to the light motors - the power for the lifting motor coming from a different circuit.

Does that alleviate the concern somewhat?

Thanks
Gavin


Ah, that is a bit better, only a small extra current through the stalk switch. It's still a daft arrangement by Lotus though. :D
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PostPost by: billwill » Sat Oct 26, 2019 9:53 pm

lotusS2guy wrote:Painless Performance sells a kit that adds relays and fuses to both high and low beams. it is prewired so that only relay current goes through the headlight and dip switches. I've used it on my Elan and my wife's 280ZX and it does the job.

https://www.summitracing.com/parts/prf-30815


That looks good, but is an expensive way of doing what only requires a few extra wires really as the headlight bulbs already have relays, just that they are wired in a daft way.

OK for those who don't understand electric circuits (didn't pay attention in physics classes in school ? 8) ) Probably cheaper than getting a 'garage' to do it for you, but lots more expensive than doing it yourself.

Mind you I still haven't gotten around to rewiring mine through all 52 years of owning my Elan. But that's basically because if I start doing that I would want to make other changes to add extra fuses and put almost all the dashboard/stalk switches through relays.

I bought the fuseboxes some time ago, but haven't changed any wiring yet.
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https://cpc.farnell.com/multicomp/ppfh- ... fuse%20box
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PostPost by: gav » Sun Oct 27, 2019 9:54 am

Be careful what you wish for - I'm running 4 fuse boxes at the moment - two were introduced when I replaced the loom, one is an auxiliary for all of the non standard bits and bobs and the 4th is dedicated to the ECU which has its own dedicated supply completely independent of everything else.
Admittedly the two additional boxes are only 4 fuses each but I didn't want to interfere with the original circuitry or I'd end up with a bespoke loom and wiring diagram. I did want a fuse for every circuit so that I stood a chance of understanding what has failed.
When I started the build I understood even less about electrics than I do now - and my current knowledge (sorry) is pretty basic so I took the cowardly route...hence the overkill.
Three live under the glove box out of the way - but it is a bit like spaghetti junction. The 4th is by the ECU which is on the drivers side just above the top door hinge.
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PostPost by: billwill » Sun Oct 27, 2019 1:50 pm

Nowt wrong with bespoke loom & wiring diagram, provided that you ensure a copy gets sold with the car if it is sold on.

Much better than trying to guess which of the many published wiring diagrams relate to your car. My car came with 4 fuses from the factory and the published wiring diagrams don't fit.



~~~~~~~

PS: my degree is in Electrical Engineering, which included lots of mechanical engineering and was obtained in the same place (UCL) as Colin Chapman's had been obtained some time earlier.
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PostPost by: gav » Sun Oct 27, 2019 2:18 pm

Bill

I'm envious of your degree - I think mechanical can be learned with experience and an enquiring mind because when things aren't working, you can often get a feel for the likely causes.

Electrics is a bit of a dark art to me because you join up some wires and it either works or goes pop - and that's the end of that (generally)! Spoken like a true (frustrated) amateur. :oops:

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PostPost by: gav » Sun Oct 27, 2019 8:45 pm

Had a think and a ferret and come up with a plan. The slight difficulty is that I have as pair of blue white and a pair of blue red cables linked in the fuse box each with a 15A fuse. What I don?t yet know is whether this was originally one cable that has been split to get to the fuse box or whether they follow different routes. I suspect the former so will have to work that out.
The plan is to set aside all of the current relays and replace them with a single 30A switching relay with a clean power supply and switched by the dip and main signals from the switch. The flash cable can go to the main beam switch side so that it turns off the dip when used.
I will abandon the flashing unit and all of the associated wiring and have configured the lifter to trigger when the switch goes from side to dip.
The loom was set up by an auto electrician. With this is in mind, would splitting a cable and linking it to a fused supply protect the circuit or is it more likely that there are two cables running in different directions?
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