Headlight Switch Wiring

Staytite said:

Functionality required is for lights to work, as in side/rev&speedo on one toggle position and dip/main/rev&speedo on another.
The rear/brake lights are fed from the ignition switch.

Am I missing anything?

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As maylar says, the headlamp switch on '71-'74 models would normally be a two-position switch that toggles the headlamp ON-OFF when the ignition switch is at the 'Ignition and Lights' position. All lighting (Park, main lighting) is fed from the ignition switch terminals 3 and 4.


As gtiller said, pre-'71 models had a three-position lighting switch as they had a two-position ignition switch.

Staytite said:

Toggle towards tab 1 = Tab 1 connected to 6, 7
Toggle central = Tab 1 connected to 4, 6, 7
Toggle towards tab 7 & 8 = Tab 1 connected to 4, 7, 8

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Probably 31788

here's a pic of my 74 -

didn't do much, but clean things up a bit and add some zip ties...



sorry - didn't realize this was an old thread....

Yes, the Lucas 31788 57SA is what is fitted to the pre-71, so the wiring diagram and pinout should stack up.

Thanks to all

I think an advantage of using the three position switch is to utilise the extra tabs to reduce the
number of three/four way cable splits and thus the number of wires within the headlamp shell.

Joe's wiring is very neat and tidy which is what I am trying to acheve.

I like the simple wiring of G Tiller's wiring diagram above. It is very close to what I am doing.

I rather like feeding tab 4 as it frees up a tab for my solid state voltage/ignition on unit.

Tab 1 to solid state voltage/ignition on light
Tab 4 feed from ignition switch
Tab 6 to side light
Tab 7 to rev & speedo
Tab 8 to dip/main switch

Thanks

Staytite said:

Tab 1 to solid state voltage/ignition on light
Tab 4 feed from ignition switch

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If tab 4 has the feed from the ignition switch then tab 1 (solid state voltage/ignition on light) won't have power at switch position 1 unless that's your intention?

Hi Lab

Although it was not my intention to have an off position when the toggle switch is in position 1, ie on the tab 1 side, I did notice it

An interesting interesting "accident" as a result of feeding into tab 4

My main purpose in using the 3 position switch I bought ages ago is to reduce the number of wires, and especially the multiple connections
within the headlamp shell. As you say, I really only need a two position switch to turn the headlamp on/off, but that only has two tabs.

And I'd need to buy another "correct" switch. Much of my Commando is not correct for 1974, including the wiring. For instance; I do not like
to rely on the bars, HL shell, frame, engine, mudguard etc as forming the earth connection.

I quite like the thought of having an everything off position for the toggle switch even though I cannot see a practical necessity.

Thanks

Staytite said:

Much of my Commando is not correct for 1974, including the wiring. For instance; I do not like to rely on the bars, HL shell, frame, engine, mudguard etc as forming the earth connection.

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The Commando electrical system doesn't use the HL shell as an earth/ground/return to the battery(+) although the connector at the bottom of the shell is often mistaken for a 'headlamp earth' it's there to provide an earth connection to the harness (red) for the front indicators.
The system of red wires running throughout the harness is the actual electrical system 'earth' and not the 'frame'.

You will probably find that the wiring complexity won't be any less using your switch compared to stock wiring. The warning lights still need to connect to the appropriate wires, and the brown/green "lights on" feed wire connects directly to the instrument lights and pilot light. I don't see how adding a switch can simplify that. Look at Joe's post above and see that just one pair of switch contacts are needed unless you want to do something funky.

I'll also add that the 3 position switch is big and may interfere with an LED headlight if you choose to use one. I had to bend the unused contacts on the bottom of my switch to clear the H4 LED that I'm using.

Bringing up an old thread here so I don't start a new one. Is it a reasonable solution to connect the blue and blue/yellow wires to leave the headlight on to bypass a dodgy switch?

Wonky said:

Bringing up an old thread here so I don't start a new one. Is it a reasonable solution to connect the blue and blue/yellow wires to leave the headlight on to bypass a dodgy switch?

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Sure, that's all the switch does.

The lamp switch is somewhat redundant when you have three position keyed ign switch. It can ha ve just running lights on or both running and head light on (as long as lamp switch is also on or bypassed as suggested). Having the lamp switch working just means easier to access lamp control while riding.