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hi does anybody have a wiring diagram for this alt, i have the ground hooked up and the the power, there r 3 other terminals also, does anybody know what these are ,thanks ken

Do you perhaps mean the Delco 40si?

If so, this is actually a family of alternators (now discontinued), and we would need to know which specific model you have to advise you.

That being said, the other three terminals (and their functions) are likely:

"I", "IGN", or Terminal 1: This connects to the master switch ("Ignition") and tells the alternator to "turn on".  Note that the 40SI is excited from the B+  or main output terminal, so this must always connect directly to battery (and thus can not feed the center terminal of an isolator, unless the isolator is equipped with a special exciter terminal).

"B", "BAT", or Terminal 2:  This is the battery "sense" lead and should be connected directly to the + terminal of the battery.  This is separate from the larger main output, which also usually connects directly to the battery.

"R", "Relay", or "AC":  This is a half-wave rectified AC signal at roughly half the rated voltage of the alternator.  It's purpose is to drive the coil of a relay which will activate or deactivate items that should only be on (or off) when the alternator is running, such as the "Not Gen" or "No Charge" lamp.  The AC nature of this signal makes it useful for driving tachometers as well.

-Sean
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