My brother owns a 2000 dakota 4x4 3.9L. He was having a starting problem. Truck wouldn't start. Just clicked like his battery was bad. He checked his cable connections at the battery and found both battery terminals were cracked/broken. He bought new ones and installed them to both cables. When he went to hook them to the battery, his starter cranks the motor over. What could be the problem? Starter, solenoid or ignition switch? Or how to isolate what is going on?

 

In the PDC, the fuse box under the hood, is a starter motor relay. Pull that. This relay "trips" the solenoid on the starter motor.

If it keeps cranking it is the starter. If it stops, it's either the switch or the relay.