there is a very good download available if you go on www.thetford.eu and go on 'Ask Thetford'. They promise a reply a reply in two working days but that has not been my experience. I think you can get the download from their site by going on to 'brochures and handbooks'. I have emailed customer care at Thetford telling them that they have a huge problem or a massive design fault, judgung by the number of people with thetford flush/switch/pump problems on this website alone. Just a shame they seem to have a monopoly on caravan fitted toilets and seem not to care about customer problems. Hope this helps. The actual instructions on how to fit a new switch are quite good.
Ivan Cox
April 2008