I would think that the first thing your dealer checked was the IC pump and sensor since they are so much cheaper but you never know with Chrysler dealers. My dealer told me that they applied voltage to the supercharger clutch but it would not engage, so that's how they determined it was bad. Didn't sound overly technical so perhaps your dealer did the same.

As for the $100, you paid that to have a problem fixed. The problem has not been fixed so you can argue that the $100 still applies to any further repairs and/or parts.