I took my wife's C280 out for a ride. Opened the sunroof in the back. It went up only a little bit. So I figured, it's been closed all winter, maybe it's just a bit stuck. So I close and reopen, but it only opens a liitle. The roof slides back and forth fine, but won;t pop up like it should.

What makes it pop up in back and how do I diagnose / repair?

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport