[FC] "generator " light

[Joel McGregor]

Late models have a diode & you don't need a different bulb.  I accidentally took diode out ('65cv) when I switched from the stock alternator to an internally regulated one.  I had to put it back in but don't remember all the symptoms.  One was that the car kept running when the ignition switch was turned off.  I have an MSD and fuel injection so that may not happen on a stock one.  The diode keeps the current from going the wrong direction.  The bulb supplies 12V to the alternator to trigger it.  The diode keeps the 12V from the alternator from feeding back through the bulb.  As someone else said it is correct that they have 12V on one side when you turn on the key which supplies the trigger to the alternator.  When the alternator starts working it will have 12V on the trigger wire which causes the bulb to go out.  12V on both sides of the bulb gives the bulb 0V.
Joel

> Somebody else will know better but I seem to remember that something had to be done with the bulb. Like maybe there were different bulbs for generators and alternators... different resistance maybe. Solution was to add a resistor or diode or something. Again, my memory is very foggy and likely wrong on this. Maybe one style had switched ground and the other was grounded and had switched power. Might be wide range in what works vs exactly how it should be. Hundreds of good articles online rearding the proper wiring of charging systems but it isn't real exciting reading.