Thank you Tom Smith, I tried this to fix the original posters problem and it worked a treat! Cheers!
Mark Houston, December 2011
Top cover needs to be removed. 2 screws at the back and then pull the cover back. Then remove side cover on the left side (As you look from the front) A couple of screws vertically and one inside the top (to loosen a retaining bar) The float is inside a white plasic box at the bottom. You need to unclip the wires and lever 2 small retaining clips on the box and then it will slide out. Plastic float and box can then be cleaned.
Tom Smith, May 2011
there is a one way valve and a float switch in the side/back of these.they can get blocked with fluff and need cleaning out.need to remove part of the back panel and possibly the left side panel (as you look at it from the front) to gain access
