[johnta1]

The 4 pin plug has connections marked S, F, L and P. NOTE: If your alternator as an 'I' in place of the 'L' connection, see the paragraph below.

S = Sense
F = Failure (Indicator)
L = Lamp
P = Pulse

The 'S' connection connects to a remote voltage sense location. This wire connects to the larger gauge wire that was on the stock SI alternator connector (Not the thick battery wire that connects to the rear of the alternator). As it sounds, the alternator uses this connection to sense the remote voltage to determine if it's sagging (more current required), or not (less current required).

The 'F' connection is the failure indicator. It normally would go to a alternator failure indicator in some setups (as opposed to an alternator lamp).

The 'L' connection is the lamp connection. The 'lamp' refers to the typical idiot light for an alternator. This connection requires switched (ignition) voltage through between 35 and 350 ohms of resistance. If the alternator sees below 35 ohms of resistance, the CS alternator will fail eventually.

The 'P' connection is not used in your application. It's a pulsed output that connects to a tachometer in some applications.

For alternators that have an 'I' connection in place of the 'L' connection, the wiring requirements are a bit different.

This is what I have saved.

["QUICK-SILVER"]

Originally Posted by johnta1

This is what I have saved.

2nd and 4th terminals are the ones you don't need/use.

Went and found this site that covers it pretty well and explains about the amount of resistance on the light wire.

http://www.novaresource.org/alternator.htm

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[ARAMP1]

Thanks for all the info gents! My truck that I'd be using this in is a diesel. I wonder if there are tachometer's out there where the Pulse lead could be made to work.