Topic: Charging system FUBAR

[Jeffy]

Ok I just finish swapping the ALT with a new one. Connected all the wires IAW the instruction in the ALT (no by pass or rigs) I have 13V out of the ALT when it meets the BATT drops down to 12.20V when the fan (electric) kicks in goes to 11.90v and very slowly goes back to 12.20 if I take all the loads off from the electrical system and let the engine idle I get 12.50+- If I use the lights, forget about it it keeps droping at a steady rate. What is going on what is regulating the current? Is it the right ALT?

4 new ALT (3 burn out)
2 new BATT
1 Starting relay
1 ECU
2 week of troubleshooting
3 days of miss work
4 times stranded in the road without juice
and countless suggestions from IDIOTS recommending to sell or burn my jeep

It's hard to test a alternator without doing a load test.  You can usually get Auto Zone or  other auto parts store to test it for you.

Think if it this way, once you get it fixed it will be solid!

[oldjeep]

So you have wires attached to all 3 terminals of the alternator?  The output on the back and the 2 regulator wires on the side?  The correct alternator is internally regulated.

It sounds to me like one of the regulator wires is broken or corroded.

[aw12345]

A short of some sort or the starter keeps running. I would buy a cheapy inductive amp gauge from a auto parts store. its a cheap diagnostic tool that you can slip around wires. you slip it around the charge wire when running with all accesories on/ ie lights heater and so forth it should show a positive charge. Next with everything turned off see if there is a battery drain with the amp gauge. This should give you an idea of what is happening. If it is lack of charge but when tested at the store and the alternator does work start looking at the wire that excites the alternator or poor alternator ground this you can figure out with a volt meter. Same goes for voltage drop across the charge wiring  and all ground wires from body to frame to engine. I hope this helps.