Alternator

[dannytrigger]

Is it possible to use just the one wire straight to the battry if i dont need/want the warning light?

[twiss]

No sorry,

The warning light wire also provides power to the alternator.
When revs are low, the alternator requires some leccy to charge the electromagnets in it.
(I think lol)

If you dont use the battery light wire, the alternator will only charge when over 3000rpm-ish

[kibris]

No sorry,

The warning light wire also provides power to the alternator.
When revs are low, the alternator requires some leccy to charge the electromagnets in it.
(I think lol)

If you dont use the battery light wire, the alternator will only charge when over 3000rpm-ish

You sure Twiss? I am in the middle of a rewire on mine, there are 2 wires coming from my Alternator a black and white one which has to be connected or alternator did not charge and a red and white one for the idiot light - mine is charging with the red and white disconnected.

or seems to be

[twiss]

Yeah thats definitely how it is on my original Samurai alternator (mistubishi one), and the one have now (denso i think)
Might be worth checking it with a multimeter, cos this stumped me for a while!

[twiss]

Here we go, Wikipedia can word it much nicer than I can but the principle is correct:

The field windings are supplied power from the battery via the ignition switch and regulator. A parallel circuit supplies the "charge" warning indicator and is earthed via the regulator.(which is why the indicator is on when the ignition is on but the engine is not running). Once the engine is running and the alternator is generating power, a diode feeds the field current from the alternator main output equalizing the voltage across the warning indicator which goes off. The wire supplying the field current is often referred to as the "exciter" wire. The drawback of this arrangement is that if the warning lamp burns out or the "exciter" wire is disconnected, no current reaches the field windings and the alternator will not generate power. Some warning indicator circuits are equipped with a resistor in parallel with the lamp that permit excitation current to flow if the warning lamp burns out. The driver should check that the warning indicator is on when the engine is stopped; otherwise, there might not be any indication of a failure of the belt which may also drive the cooling water pump. Some alternators will self-excite when the engine reaches a certain speed.

[kibris]

mmm that is strange as I said mine "seems" to be charging - I have put a volt meter on the battery and it reads 12 Volts when engine off, but 14volts with engine running - thats with black and white connected but red and white disconnected.... I was just going to use a voltage gauge and not bother connecting the light - but having now read that I will connect both up just to make sure.

thanks

[twiss]

Yeah it could be that you have a slightly different alternator, but checking it good...
Worst thing ever running out of battery on a cold wet night!

[dannytrigger]

mine only has one wire running direct to batt? and the muppet who had it befor me must have had a coil of red wire in the shed as every other wire under the
bonnet is red!!!

[kibris]

mine only has one wire running direct to batt? and the muppet who had it befor me must have had a coil of red wire in the shed as every other wire under the
bonnet is red!!!

lol - what a muppet he must have been - mines all black

[dannytrigger]

is it just a cas of running another live from ign barrel
then?