Hey All... Im sure everybody else is at the NATS! I had to work this weekend and my Jeep is being Chevylike this weekend...

Anyway It is sometimes charging at 14 Volts on the Guage then it will act like it Quits, drops down to 12-12.5 volts, then it will charge again. I took the alt off and took it in to Advance Auto, they tested it and it tested good..

So I figured battery must be bad, had battery tested. Rated at 875 CCa Only tested at 443 CCa , so I replaced the Battery... Guess what Still does it but now is staying at 12.5 volts and seems like alt isnt charging..\

So My Question is: Does anybody know

• is this internally regulated?
• What "Excites" The alt to start charging? Is it compueter controlled?
• Is there a relay or fuse or anything between the power that excites the alt and the actual windings? Thanks

2000 Grand Cherokee 4 Liter I6

You have a week-old PM to reply to...

Could be worn brushes in the ALT. could be making contact and then lose contact. Next time its acting up rap it with a small hammer and see if it starts charging.

I'm thinking part time "open". I'd check all your connections for clean/tightness & clean the ECU ground as it could be marginal & intermittently making/breaking contact w the fender or firewall. Block grounds also

OK Ive been racking my brain on this thing for awhile now. I Disassembled alt, brushes were good, I traced all the wiring clear back to the PCM everything was good , cleaned all grounds. Replaced Battery, Battery temp sensor, alternator, and still no charge. Only thing I could figure was the part of the PCM that acts as the "Voltage Regulator" is bad.

Long story short dealer wants big$$ for a new computer and to flash all my info onto the new one, found one used for $200 But Dealer still must program it to my car.This thing has 130,000 mi on it its no jewel..

Did some research on the charging system, found that it is the same basically as the post '70 Mopars. Negative field wire is interrupted by the PCM to contol voltage at 14.5...Just as the voltage regulator does on our old mopars.

So guess what? Under the hood of my 2000 Grand cherokee, right next to the PCM resides a Mopar Voltage Regulator. Works like a charm. Just ran the Red wire on the VR to Ignition Hot, and the Green from the VR to the -Field trigger wire on the Alt. (Green) Left the Alt Source wire to the PCM alone (Lt. Blue/Black) So the PCM still reads alt output, and everyones happy.No Codes either!