2006 Dodge Caravan wont start

If that is one single, rather loud clunk from the starter each time you turn the ignition switch to "crank", that is typical of worn contacts in the starter solenoid. That used to be a real common problem with the little silver Nippendenso starters, but your van uses a different design that has less trouble.

Start by measuring the voltage between the engine block and the large battery terminal on the starter solenoid. You must find full battery voltage there, 12.6 volts. Keep measuring while a helper tries to crank the engine. Normally it will drop to around 10 volts while it's cranking. If it goes real low, the battery is bad, or more commonly there's a loose or corroded connection in one of the large battery cables. If the voltage stays high and it doesn't crank, suspect worn contacts in the solenoid. Move the meter probe from that battery terminal to the other large solenoid terminal with the braided cable under it. You will see 0 volts there at first. You should find around 10 volts during cranking. If that stays near 0 volts, replace the solenoid or entire starter.