I have a TON of PMs about charging system issues...
So here goes,
DELCO SI ALTERNATORS IN AMC JEEPS,
(Or being swapped into older Jeeps)
You need THREE connections to the SI Series alternators,
1. BATTERY (BAT.) on back of alternator case.
This should run to the POSITIVE battery cable at the starter relay/solenoid.
This is the closest SAFE point to the battery you should connect.
Connecting from alternator 'BAT' terminal with 10 Ga. (or larger) wire at the alternator 'BAT.' terminal,
Running to the FUSIBLE LINK just before the starter relay/solenoid.
1a. FUSIBLE LINK is a fuse wire intended to protect that wire to the alternator, so the fusible link will be the first 5" or so from starter relay battery terminal connection, then 10 Ga. wire, then alternator.
Fusible links are $5 and SHOULD NOT be left out of your harness!
If that primary charging wire gets against headers and burns through the insulation, the fusible link will keep your Jeep from burning down.
If you short out the 'BAT' terminal when working on the alternator, that fusible link will keep your Jeep from burning down.
If the alternator grounds internally (Fails Catastrophically) that fusible link will keep the vehicle from burning down.
2. The 'Sense' wire.
The sample of line voltage (Larger of the two small wires at the two wire plug) will tell the voltage regulator to produce more, or to stop producing.
Ideally, this should be a clean battery sample, since the alternator is there to charge the battery.
You can't SAFELY connect directly to the battery, so taking that sample from the battery cable side of the starter relay, or even from the 'BAT' terminal on the back of the alternator will work.
3. The 'Excite' wire.
The excite wire MUST be a key switched source or it will run the battery down.
Most times, that key switched source is from the same line that feeds the ignition, since when the ignition isn't running, the alternator isn't charging either. Shut one off, they both shut off.
Now, the 'Excite' wire needs some way of NOT back-feeding the ignition.
Since the 'Sense' terminal DRAWS current when starting the charging process, That terminal will become 'HOT' and feed the ignition if you hook up to the ignition.
Enter the Resistor Wire.
Usually stiff, Brown or Black in factory harnesses, and found in the last few inches before the two wire alternator plug, this wire chokes off enough current to keep the alternator from powering up the ignition once you start the engine.
You CAN replace the resistor wire on a Delco SI alternator with a diode.
Diode is a one way electrical 'Gate Valve', letting current reach the alternator but keeping alternator current from back-feeding the alternator.
YOU CAN NOT DELETE THE RESISTOR FROM A DELCO CS ALTERNATOR HARNESS!
DELCO CS WIRING.
Pretty much the same thing,
A larger wire to the 'BAT' terminal on the back, with fusible link,
A 'Sense' or 'Sample' wire to the voltage regulator,
BUT! A CS MUST HAVE AT LEAST 75 OHMS OF RESISTANCE ON THE 'EXCITE' WIRE TO SURVIVE.
This is VERY easy to do with a single resistor from Radio Shack built into the wire/plug supplying the alternator.
If you have switched to a CS and you keep having to replace regulators, the it's time for a resistor in the 'Excite' terminal wiring to keep the new one alive.
Many people have told me they have 'No Problems' with a direct wiring of the 'Excite' terminal, but I've never see that first hand, and I don't know of a single application from the factory that doesn't have at least 15 Ohms of resistance in the 'Excite' line. (15 to 75 Ohms, and EVERYTHING works with 75 Ohms)
If you look VERY CLOSELY at the CS regulator connector collar, you will see...
S, I or F, L, P
on the connector collar. It's molded into the plastic, but VERY hard to see some times...
P is the 'Sense' wire, or line voltage sample,
L is 'Lamp' or 'Excite' circuit,
And the 'BAT' terminal on the back is for the 10 Ga. wire.
L terminal needs between 15 and 75 Ohms of resistor,
An 'Idiot' light on the dash that produces between 15 and 75 Ohms of resistance. If you DO NOT have an idiot light, add a resistor.
This has PERSONALLY worked for me for the last 40 years, on hundreds of vehicles without failures...
(remember, I used to own an alternator/starter/battery shop and I rebuilt starters/alternators every day for over 5 years)
Hope this helps clear things up a little for the ones having issues, or anyone thinking of switching over.