The 100HE pump is inside the boiler on the right hand side. Power down, Remove the 2 screws when the flap is down and the whole cover lifts off. Slacken 2 screws underneath and black panel folds forward to reveal pump. Take screw out of end of pump and use screwdriver to check it spins. Power up and see if pump is working (vibration).
Steve.
December 2008