99 323IS electric window problem

Have owned since new and have had problems with the window interminently stopping half way down when the auto down is activted. It did this when it was under warrently and I think the dealer replaced a sensor but I'm not sure. Today it doesn't go down at all and I hear a faint clicking in the door when I press the switch. The window also doesn't move up or down to seal when the door is opened and closed. Appreciate any help on how to trouble shoot this problem. Thanks in advance, Gary