A resistor in the field wire is only to compensate for the idiot bulb blowing. When the car is wired at the factory, a resistor is installed PARALLEL to the idiot bulb. That way, if the bulb blows, the charging system will still come on as usual.

The wire at the alternator just gets "key power" if you are using a volt gauge or amp gauge (noooooo!!!!)

Hope it helps...tech note: take your NEW alternator and have it tested BEFORE you wire the system. That way you know if the system failed, or if it was a bad alternator. it's been known to happen.