Ford Repair: Starter, starter solenoid, taurus 3

Question
i installed a starter on a 97 ford taurus 3.0 and it started real good but after a while it start trying to crank on its own.  what do you think the problem would be.  I had just bought the starter at a store and it also drained out my battery doing that


Answer
The ignition switch in the steering column applies power to the starter solenoid when the key is turned.  The solenoid then completes the circuit between the battery and the starter.  

Either the ignition switch is shorted, stuck, or binding and applying power, OR the solenoid is bad.  You could also have a wiring problem.  

Hope this helps,

Dave