I have a Hogwarts Express train set. 2001.  I do not have any manual with it.  The set was used only once. The set is complete As originally packaged except for that the power pack knob seems to be missing something, like maybe a lever ?

Problem is when the train will not run. I checked all connections with an ammeter and all are working. Checked the outlet, the controller, the pins on the controller, the connection to the track and the loco itself, all are live - have power going to them.  Why then won't the loco run?  Could it have something to do with the power pack knob missing that lever part?  When I turn the knob it makes no noise at all, almost seems like it is not doing anything. 

Also, it seems like there is very little to none information about this particular train that Bachmann made! Why is that? 

Thx for help.