00 durango 4.7L the alt. wasnt charging the batt. so i replaced both. alt. still not charging the batt. tested the new alt. on the vehicle and it came back as a faulty regulator. removed alt. and tested it in autozone and passed. pulled one off the shelf and it passed.what is going on? when i pull the pigtail plug off the back of the alt. nothing happens whiule its running, could it be the plug is bad? anythingelse?

 

Check wires at the battery and make sure they're not corroded or frayed and next make sure the fuses are in tact in the main PDC.

 

Just for the hell of it I changed the alt fuse. And still nothing. the wires don't look bad at all no corrosion or fraying aside being a little dirty from road grime they look almost new

 

If the connection from the alt. to the battery is solid, then it's the regulator on the alt. not telling it to charge. Now there are quite a few sensors and conditions to be met that tell the alt. to charge the battery or not, mostly your battery temp sensor. I can't recall off the top of my head all the conditions but they will be listed in the service manual. For toubleshooting more yourself, a voltmeter will deffinetly help you out from this point on to trace where there's power and where this isn't.

 

You need to test how many volts are being generated at the alternator. Then see if that voltage is making it to the battery. If not then you have a burned main wire. If not then check the volts going to the alternator to ensure that the rectifier is getting 12 volts, if not then check the ignition switch and relays.