Mike,
I'm not real sure what type of system you have so this might be bum info. The idiot light has two wires attached. One wire is hooked to a switched contact on your ignition switch...it becomes powered when the key is turned ON.
The other wire from the idiot light goes to DA terminal #1 if it a internally regulated alternator. When you turn the key switch ON, it powers DA #1 to get the alternator charging...this also makes the dash light illuminate UNTIL the engine starts and the alternator begins charging...then the little dash light loses its ground and goes out. This means all is well with the charging system.
If you are using a generator, the same wiring applies except the wire from light to GEN goes to the ARM terminal on the generator. When it starts to produce voltage, the light goes out.
The dash light should have two wires...one goes to the ignition switch (battery) and the other goes to either the ARM (GEN) or to the #1 tab on the little DA plug in back of the alternator. This is a internally regulated alternator, not one with a voltage regulator mounted somewhere.
Does this make sense?
Stuart