12V feed to alternator

[steg1970]

The 12V feed to excite the alternator on starting has stopped working. I examined the rear of the clocks/dials and found the laminated copper strip was broken. I've tried to resolder it, without success.

As an alternative is it possible to wire a small switch on the dash, connected to switched 12V and feed it directly to the alternator exciter? So when the engine is running I just give the switch a quick flick to get the charging going then switch it off again.

Are there likely to be any problems? i.e. am i effectively putting a short on the battery or will the inductance of the flux in alternator rotor limit the current flow.

Thanks

[Guderian]

I didn't even know alternators operated in this way; maybe i am missing something but i thought them to be a self contained charging unit with their own regulator so as soon as they start to spin they deliver the appropriate V/I depending on the charge state of the battery and the demand on the system. (so i have probably learned something today...!)

I do know that on some vauxhalls the wattage of the red ignition light has a direct effect on the low speed 'cut in' speed of the alternator.
Hence changing the bulb varies the cut in. Not sure what happens if the bulb blows though.... possibly a 'no charge' situation...?

[AlexW]

The alternator only has 2 connections, one for the light (gauge on 6-dial clocks), other for the red live.

Why is this a problem anyways?