Alternator dummy light

[Paranick]

hi Guys. I have a 454 bbc marinised motor in my boat. I purchased the boat from the previous owner and the alternator was broken so I replaced it with a standard gm 3 pin alternator. but when I plug in the purple wire that goes to a relay the motor won’t shut off. Also I have no idea how to run the dummy light as there was never one set up as the previous owner messed around with it.
My question is why does the purple wire stop the motor from turning off and how can I fix this also how do I wire the dummy light from the relay. The relay also powers my distributor and fuel pump.

 

[Lucien Nunes]

It sounds like you have the indicator wire directly connected to the ignition feed, so that all the time the alternator is running, the excitation rectifier is back-feeding the ignition / fuel pump relay when you turn the key off. AFAIK on a GM 3-wire, this is pin 1 on the regulator. Connect the indicator light, and if necessary, a parallel resistor to total a couple of watts at 12V, between pin 1 and the ignition relay output. Turning the key on lights the indicator while pin 1 is dead, and sends a trickle of current in to provide some excitation. When the alternator kicks in, pin 1 goes up to near battery volts so the light goes out, and it provides its own excitation. Pin 2 should connect directly to the battery feed as it is the voltage sensing wire.

 

[Paranick]

It sounds like you have the indicator wire directly connected to the ignition feed, so that all the time the alternator is running, the excitation rectifier is back-feeding the ignition / fuel pump relay when you turn the key off. AFAIK on a GM 3-wire, this is pin 1 on the regulator. Connect the indicator light, and if necessary, a parallel resistor to total a couple of watts at 12V, between pin 1 and the ignition relay output. Turning the key on lights the indicator while pin 1 is dead, and sends a trickle of current in to provide some excitation. When the alternator kicks in, pin 1 goes up to near battery volts so the light goes out, and it provides its own excitation. Pin 2 should connect directly to the battery feed as it is the voltage sensing wire.

Are you saying the light goes in between the alternator and relay. Have you got a diagram I can follow. I am very new to this