Double switch for high/low beam activiation - Help needed

NiekN

NiekN

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Hi all,

I'm currently designing the new wiring system for my '74 CS rally car and I'm in need of some help. I'm trying to activate the high/low beam using two seperate switches, in that I want to keep using the stalk on the steering column but also have the floor switch installed. So far I've got it working only in a way that the low beam remains on whenever the high beam is active, but in theory the low beam should be off at that point. Does anyone have any idea as to how I should wire this system, if at all possible? I'm using seperate relays for both high & low. Thank you in advance!

Kind regards,
Niek

PS. I'm running the full restoration on my website and YouTube channel; If there's enough interest I'll post it on here as well. (for the purists among us, this is not a factory standard car when I'm finished).
 
If you connect the ground side of your low beam relay activating circuit to pin 87 of your high beam relay- your low beam relay will be inactive whenever your high beams are on.
 
There are few ways to realize it.

In general all the switching should be performed on low power side (relay coil).

You can use dual relay for high beam, which will disconnect lower low beam relay coil (1st part) and switch on current on high beam lamps (2nd part)

Is the switching off the low beams required to get MOT in the UK? Just asking.

I would love to see your YT with full restoration. I was looking once for good, comprehensive one, but failed as most of them were just to general, to short or ending at some point without following up.
 
If you want the low beams on when the low beam switch is activated, wire it directly to the low beam relay. This will power the low beam filament in the lamp whenever it is on. Wire the high beam switch directly to the high beam relay and this will activate the high beam filaments when it is on. If both switches are on, all filaments will be powered. This might have a negative effect on the dual filament bulb in the outer positions because of the heat generated with both filaments powered.
 
Hi Guys,

Thanks for all your inputs. I've provided individual answers to each of you (hopefully I didn't miss anyone/anything). Below that I've added more to my question and restoration in general.

@sfdon: I'm not sure I fully understand what you're suggesting with combining the ground of the lowbeam to the relay of the highbeam; wouldn't that shortcut the circuit? Yes, I'm using 4 H1 bulbs, or at least that's the plan.

@Krzysztof: with a dual relay, do you mean a change over relay? I don't need an MOT because of the car's age, but as fas as I'm aware its the general requirement in EU (and assuming the UK as well). In order to register the car I have to pass a minimal road worthy test, which is pretty much an MOT.

@Mike Goble: I like your idea of direct wiring, but that leaves me with the issue of not being able to turn off the low beam automatically whenever activating the high beam, unless I'm mistaken?

-------
In the meantime I've made a quick drawing of my setup; the first photo (drawing) shows how I think I can solve the issue with a chage-over relay. That being said, I don't know how to control this with 2 independed switches, because at any given time, it'll be provided with a signal for the high beams to be on from either the switch or pedal (unless both are in the off position). The second image (computer drawing) shows the setup I have with using two independed relays, which brings me back to the auto-shutdown of the lowbeam as well as the 2 seperate input sources for the high beam.

I apologise if I have misunderstood any of your replies, please understand my wiring knowledge is basic and I'm trying to learn & catch up as I'm going along. If you could provide any (simple) drawings with your replies it would be hugely appreciated as it gives me a better idea of what I'm actually trying to wire up.

With regards to my restoration and YouTube series, I'll get this going on the forum here in the next few days. Any suggestions/requests are much appreciated. My plan is to combine the videos and blog text into a thread and continue from there with an update whenever I upload something to my site/YouTube. Any photos I have will be added as well. For the time being all the info can be found here:

My car: Brünhilda
Restoration website: Project C.A.R. (restoration)
YouTube: https://www.youtube.com/c/BrunhildaE9/featured
Instagram (most updates): E9Brunhilda

Thank you.

Kind regards,
Niek
 

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how about asking you the important question- what is your goal?
do you want independent control of all 3 circuits, low, high and fog?
explain this first.

in the USA at least the 1974 lighting circuit uses the white wire from the h1 high beam bulb filament as the ground for the low beam relay. With no B+ voltage to the high beam bulb, the low beam relay functions.
 
@sfdon The goal is to be able to control the high beam by both a stalk on the steering column and a floor switch (the latter which is very useful during a rally for last moment change of lights without taking hands of the wheel). I don't plan on installing front fog ligths (rally lights are controlled by different switch/circuit all together). Hope that answers your question? I've removed all the wiring from my car and plan on constructing a whole new loom from scratch that's far easier to work with when any issues arrise.

Ps. these are road rallies, so I'll have to be able to turn the highbeam off for oncoming traffic.
 
If you want to use the floor switch to turn off the hi beams that were activated by the stalk appears to be the problem- correct?
 
Thank you @sfdon ! Final question, how to I wire this 3-way switch system into a on/off switch with only 2 tabs? :rolleyes: Run a wire from the foot switch to the column stalk and connect this wire to both the "outputs" of those switches?
 
Neik - I think your second diagram in post number 6 will work if you move the floor switch so that it provides power to the stalk switch instead of splitting power to both switches. In this way, the stalk switch would be the primary way to turn the high beams on, and you would have to get in the habit of leaving the floor switch in the closed position so as to enable the stalk switch.

The stalk switch will not turn on the high beams if the floor switch is in the open position and the floor switch will not turn on the high beams if the stalk switch is in the open position, but this would avoid the use of three way switches, which as Don suggests is the common way to wire two switches to operate independently.

The benefit is that either switch would allow you to quickly switch off the high beams; the disadvantage is that there may be times when you have to work both switches to turn the high beams on (if you forget to leave the floor switch in the closed position).
 
NiekN said:
Mike Goble]: I like your idea of direct wiring, but that leaves me with the issue of not being able to turn off the low beam automatically whenever activating the high beam, unless I'm mistaken?

Now I'm confused. Why do you want two methods of switching from high to low? If you wire up a footswitch that works, when would you not use it?
Click to expand...
 
I think I've got it sorted using the latching relay I posted earlier. As long as I use both a floor and stalk switch that are of the momentary type, this should work alongside each other:
 

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If I have this correct, you have the floor switch and a ground connected to the same terminal on the latching relay. With this setup, won't that terminal be grounded no matter what you do with the floor switch?
 
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