Hi
Had exactly the same thing! Two problems:
1) there is a fill level sensor under the top cover (left side) with a plastic pipe leading down - this has probably come off and should be secured with a jubilee clip or nylon tie.
2) the connectors to the controller (rear bottom left as you look at it) are very poor - I've replaced over-heated (blackened/melted) insulation-displacement housings with individual insulated crimp spade receptacles (automotive type). Make sure you note the wire order!
Hop this helps
Ian C
January 2008