Repair/Replace Starter?

The battery is fully charged on my 2000 E350 (186k), but when I go to start it the engine doesn't turn over.  There is a rapid clicking sound only.  I'm not too much of a garage mechanic, but this sounds like a defective starter - any thoughts on something else that might be causing this, or how to fix it other than replacing the starter motor?  Thanks!
 

its your solenoid. follow  your positive cable and you will find the solinoid. im not sure if it has 2 on it or just 1 but if 2 try using a jumper wire and cross both big wires and see if starter cranks.
if it doesnt then look on starter to see if it has one on it you will see a big bolt and either a small bolt with a wire or a end that has a plugin on it. use jumper wire to cross the big bolt and small bolt or plugin which ever one it is. if it spins but doesnt crank motor then solinoid is bad.  but if it cranks motor over then the wiring is poorly connected.  you will need to clean connections then try starting it. if the starter just clicks when using jumper then it it bad and will  need to be replaced. hope this helps you out some. and good luck.

Tommy,
 
Thanks, man.  I'll check it out this weekend and let you know how it goes.
 
-- Dan

Turns out it was the battery after all.  It seemed to be fully charged, but when I had it tested it came out defective.  The E350 started up right away with a new battery.