Totally agree with 77 lousie. Next to no resistance with LED light. Wouldn't mess about with resistors. Plenty of dash tell tale lights (globe) on the market. Problem solved. Dave

Simple solution is keep the LED and install an incandescent globe somewhere between the alternator/generator and the LED.

Any old globe holder will work as long as the globe fits it.

You don't need to see the incandescent globe it's just there to provide a load for the charging system.

Thanks Zuffen, As the LEDs are fitted in the neat little mounting in the dash, I was hoping to leave them there. Your solution will be an easy fix and should solve the problem. Thanks again.
Steve.

Whenever I change my old vehicles (Jeeps etc) to 12v I replace the generators with alternators. Nothing works until you put some resistance in the circuit and as mentioned LEDs don't do the job. Easiest way for me is just to get any old light such as tail light or dash light globe in its holder and positive wire, solder an earth wire to the holder and put it in the circuit. Does not matter what size globe. All my vehicles light up under the bonnet or dash depending where I hung it when the ignition is turned on then go off after start.

If you see the vehicle is not charging at some later date, don't panic, it probably is just the exciter globe blown. They call it the Charge Lamp in this drawing.



This is a basic alternator. There are the newer "single wire" ones and on some the terminal markings have different markings but all need these various outputs. When read with drawing above it is simple.

Google shows this as being addressed many times. All comes back to being a resistance in parallel to the LED, whether a resistor or a normal bulb. Some also add a diode for back current flow but cannot see any good reason for that in older systems.
Cheers Steve

A big advantage of having a globe and not just a resistor is the light will come on if the alternator or the charging circuit fails or you lose a fan belt