Alternator field current

[northerndefender]

I am wiring up my new alternator and need to know how large the current is that is fed  on the D+ connector.

The alternator is a lucas type A127.

The current is usually limited by the warning light bulb that comes from the ignition.  Since I am using LEDs instead of an incandescent bulb I need a resistor instead hence I need to know the current.

100 Ohms at 2W seems to be bantered around on the net but I would appreciate a current spec if any one has it.

I fired up the rover for the first time in 8 months and it sounded great ;D

Cheers

Colin

[Red90]

Are you not using a 12V LED? If not the resistor is set to get the voltage and amperage that is set by the LED specs.

Keep in mind there may already be a diode in the line depending on the year. That will cause a voltage drop which will affect the LED.

[northerndefender]

The led on its own will not provide enough current to activate the regulator so a parallel resistor is used.  This is a popular circuit but I think there is an implied current limiting resistor in the LED...

The issue came about because the reproduction lenses I am using are not rated for the heat put out by an indandescent bulb.

[Red90]

There is already a resistor in parallel with the stock bulb.  Current through the light is not required.

[Red90]

Oh hang on.  What type of vehicle are we talking about?

I guess it is a series by the picture....

The stock resistor in a Defender is 100 Ohm, 5 W.

[northerndefender]

Resistor and a bulb !  I will have to do some more digging.