Mystery switch & wire

[RamblerRob]

Hey guys.
Need help figuring out what this switch and wire might be for. Truck has been heavily rewired.
Its a simple on off switch on the lower right dash of an s2a. Probably not standard.
It gets power only with key in start position. Has a long wire that can reach the front of engine bay or back to about mid truck.
Truck was running a naturally aspirated diesel engine previously.
Any thoughts on what it might be for?

[BjornErickson]

fuel pump?

[RamblerRob]

But its only live when the key is in the momentary start position not the run position. Not sure if fuel pump would make sense

[RamblerRob]

Also. In addition to the key start position to crank there is a separate crank switch (i assume) in center dash. So maybe someting to do with glow plugs?

[Rob]

Lots of possibilities... heater motor, electric radiator fan, power supply to a relay for auxiliary lights, interior lights, back-up lights (examples of what my series rovers have had)...

[RamblerRob]

Do any of those make sense to be live only on key start (not run start, just start)

[RamblerRob]

Must have sonething to do with the ignition circuit. Wires are on 12ga... Maybe 14...
Might not matter as i have to redo the ignition circuit anyway

[Rob]

Whoops, misread the post regarding the "start" position. :oops:

Now I'm thinking it is a low-tech anti-theft device, power circuit to the starter solenoid to prevent someone from starting it without flicking the right switch?

[red90]

If it is powered in a position between on and start it is for glow plugs.

[ANDYD]

I've seen a wire like that for an exciter circuit to a (non standard) alternator. Some after market alternators need a initial exciter voltage to get them kick started. :dontknow:

[RamblerRob]

My first thought was glow plugs but never dealt with diesel before. I think the ignition switch is from a petrol rrc so that might explain the muckery.

Now that i know i can put my mind to rest :)