Have you by chance checked the lighter plug with a voltmeter (set to DC) to see what voltage in being output? After doing this plug in the charger and then can test the end that inserts into the Ipod to see if any charge is being generated.

 

I put one of the Harley power points pn 91843-97 in today took about half hour. If you look at the lighter socket it has slots in it if the charger tip goes in one of the slots it will not make contact. Power point is solid body and has a nice cover.