Please could you electrickery wizards guide me.

I have a pair of 6 volt semaphores. I would like to use them on a vehicle (not an A7) that runs 12 volts.

Will I do any damage to the unit by running it at 12 volts? I do realise the bulbs will need changing.

The semaphores will only have very occasional short term use.

Location: North Herts

They'll be like semaphore indicators on Viagra

Steve

Location: North Yorkshire

They will certainly spring vigorously to attention on 12 volts !

The risk is that the double normal current at double normal volts will mean they will dissipate four times the normal heat and could burn out if left on too long, say more than 20 seconds ?

Option 1 (for the purist) is to have the solenoids rewound for 12 volts

Option 2 is to use a series dropper resistor, but try it out before doing anything permanent as they might end up a bit sluggish. I don't know the current they draw, but for example if it's 5 amps and you need to lose 6 volts then a 1.2 ohm resistor (or thereabouts) rated at 30 watts will do the job. Try Maplin for a metal cased wirewound job, you might get away with a lower rating than 30 watts for short term usage.

Option 3 is to swap them for 12 volt ones. You might end up in profit.

Location: New Forest

I had to do this two years ago on an Opal that had 12v electrics.

As John says, they popped up with a fair shunt, keep them on longer than 20-30 seconds and they start to smell very hot.

I tried a 12v to 6v dropper but they barely came up, in the end I fitted extra bulbs in line to them under the dash - wasn't perfect but stopped them overheating.

A resistor in series and equal to the resistance of the solenoid is the right way to go. You will initially get the full 12V across the solenoid when you first switch on which will quickly drop to 6V as the current increases so it should be a bit snappier coming up than when on only 6V supply.

Location: Royston Hertfordshire

Nick,
I was of the impression that 12v units are quite readily available, buy some and donate the 6v ones to me. Well you have to try don't you

Location: Oakley , hants