Help with alternator to battery bank wiring

[callumsmith52]

I am trying to wire up a Mitsubishi Alternator to my 12 volt battery bank. I have the battery positive connected to the B+ post and a cable going from the battery negative earthed on the alternator. The alternator is internally regulated and has 2 more terminals labelled S and L. Im led to believe that the S terminal is the voltage sensing terminal for the regulator and the L is for the lamp. I wired from the S straight onto the B+ post. With the L terminal i wired to a lamp then to a switch and then back to the B+ post. From what ive read when the switch is on the light should come on and once the motor starts up the light should fade out. This is not happening to my set up. Does anyone have any ideas why. Am I missing a vital wiring connection somewhere or have i got it completely wrong.

 

[Kiwi]

Sounds like you have it wired correctly.

What size lamp have you got on the "L" terminal? Should be about 2-4watt.

What is the history of the alternator?

 

[callumsmith52]

Sounds like you have it wired correctly.

What size lamp have you got on the "L" terminal? Should be about 2-4watt.

What is the history of the alternator?

The lamp is a 2.5 watt LED.

Alternator is second hand out of a working car.

 

[callumsmith52]

This is it With the B+ in the foreground with
all the wires. The earth is from the battery
and is in the background
The small brown wire is S and goes
straight to the B+. The other small wire is
L and goes to the lamp then the switch
then to B+. The biggest wire going to B+ is
the positive from the battery. Alternator
definitely sounds like its putting the motor
to work

 

[callumsmith52]

Sorry for the child like paint skills but here is the wiring diagram

 

[Alec_t]

The lamp is a 2.5 watt LED.

That may be the problem. Try a filament lamp.

 

[Kiwi]

Try it with a normal bulb.
LED's usually don't pass enough current to excite the alternator.