Posted by chris case on Saturday, July 03, 2004 at 11:23PM :
In Reply to: Wireing an Alternator...no output posted by Paul(in NY) on Saturday, July 03, 2004 at 2:24PM :
Big wire is output, goes to batt+ or ameter.
Red wire is 'signal', goes to + of battery. It tells the alt to get 13.8 at the battery, so no matter what resistance is in the wiring, you get 13.8 at battery. This is a good thing, especially if running a battery isolator that cuts the voltage by .6 in it's diode.
White wire is the "excitor", it will start the alt ouput asap. Without it it may take a minute er two for the residual magnetism of the rotor to build up enough voltage in the field. I'm not sure that a resistor is needed in that circuit, except that without one you could backfeed juice to some other accessory- maybe you wouldn't be able to turn off the engine?
4th 'pin' (I or R?) is a tap of one output winding, before the diode bridge. It makes pulses and can be used as a tach drive. Or, like on my F150, it is hooked to the choke heater so the choke is only heated when the engine is running, not while listening to the radio while waiting for SWMBO to return from "just running in to pick something up".