6v switches on on 12v setup

I found some really nice 6v switches that are original. Is it hard to use those on a 12v cmc car?

Depending on the type of contact used in the switch, it may have a maximum current AND voltage limit. This means that you wouldn't use a 6-volt switch for 12V. If there is a maker's mark and model # on the switch, you should be able to find out easily. When in doubt with electrical equipment, always err on the safe side.

Generally, the contacts in the switch don't really care that much about voltage, but they do care very much about current.

Also generally, (resistance being equal) as voltage goes up, current goes up.

So....If your 6V switch has contacts rated for 10 amps, max, at 6 volts, and you now increase the voltage to 12 volts, the contacts might not be able to handle the additional current.

But that would depend on what the overall load is on that circuit, as a lot of 12 circuits are fused for under 15 amps, anyway.

So, for instance: Let's say you found a really mint 6V headlight switch. Connecting that directly might be too much current draw for those eensy-weensy contacts. BUT! Running a headlight relay after the switch such that the switch is simply driving a low-current relay is perfectly OK. Same thing for tail/courtesy lights. Same thing for an ignition switch - just have it drive a relay that runs your ignition. Using relays in the right places can overcome any problems with mis-matched current ratings on your switches.

Awesome answer thanks

Actually the six volt stuff is more heavy duty, The contacts are under rated..

That's generally true, but why risk it? These days, you really don't know what the heck is inside those switches! Install the relays and you'll never have to worry about it.

Gordon, voltage goes up current goes down, ohm's law.
Lenny C.

Damn! You're right! How did I screw that up?

That might explain why the conductors (wires) for 6V systems are so much bigger than on 12V systems, right? What was I thinking???? You know, the body might make it past 60, but the mind is left in the dust........

But continuing the Ohm's law thing........Typically, when they changed to 12V systems, the resistance of those things being energized were changed, too, so that would require some fussing with the equation to see what's what and what the switch would have to handle.
SO! I'll stick by the observation that 6V battery wires were big, honking things and 12V battery wires are little bitty things. That says something, 'cause they needed the larger conductors to handle the higher current draw at the lower voltage.

Now I'm gonna go off and think about why 6V starters could just about turn the older engines over but the 12V systems really cranked.

So, in some cases, using a 6V switch in a 12V circuit might be OK, but to be really sure it's OK, just pop in a relay - it's very cheap insurance for the switch, no matter what.

Thanks, Lenny!

Not necessarily... Ohm's law is I = V/R, or V = IR. If resistance is fixed, voltage will go up with current.

Last year I bought a couple of 6V Bug headlight switches used. Way better quality than the China crap repro switches from FLAPS. Two out of three of those were junk out of the box!

Besides Ohms law, there is the watt formula, P=V * I, where P is watts, V is obviously voltage, and I is current. Kind of explains why 12v cars have brighter lights, doesn't it? Twice the watts at twice the voltage, current remaining the same.

Also, on the Bug specs in the Bentley manual, 1966 through 1969 ALL had 8 amp fuses in the headlight positions. We all know that VW changed to 12v in '67, so '66 cars had 6v systems. So, perfectly safe to substitute the switches, as the designed current draw should be the same, but we all know the light output was NOT. In '66 and '67, the number 1 and 10 fuses were 16 amps, all others were 8. For '68 and '69, ALL fuses were 8 amps. The reason for this was a couple circuits were changed in the fusebox and wiring loom.

If your headlights are wired for the '68 and later switch and you change to an early switch, your flash to pass feature won't work from your turn signal stalk switch. If you add a relay to put power to the headlights when the switch is off, then you can get your flash to pass working again.

Hella or bosch,, both were good.. the rest ? JUNK!!!!!!!!


I liked how some early Porsche used a horn trim ring for the horn and the horn button became the flash to pass switch,.. that was niffty toooo..