Suction for the 7901 is air being pulled through the fan inlet. This air is drawn through a seal at the right of the water tank where there is a small rectangular lint filter. Where the tank fits onto the machine itself there is a rectangular soft rubber gasket. If you remove the tank and turn on the machine there should be quite a bit of suction if you place your hand near that gasket. If the cover of the machine is off there is a plastic ducting that covers the fan motor inlet and feeds up to this rubber gasket. If this is not positioned properly you might be allowing air to enter the inlet that is decreasing the suction. The rubber seal itself may not have been reinstalled properly or the tank lid may not be fasted down properly.
Kim, January 2017
