The site : www.thetford-europe.com
First its Thetford not three ford. It could be electric valve gone faulty and if you go back to www.thetford-europe.com website click on toilets then click cassette toilet and select 262cwe it will show a list of repair video's for 250 but worth a look to see what is same on yours as some models only differ slightly. Click the left column on 260 for spares list and a pdf option is given so down load the pdf file to your computer. Then go back and look at each of the video's select what looks familiar to yours and download that to. Trouble is when you come out of each video as they are you tube video's you have to re-enter the thetford site again but its worth it to have a computer record of repairs to take with you on a laptop or whatever you have.
If you are still confused go to the foot of the screen click ' contact' bottom right fill in the form but don't hold your breath for a quick answer.
any way good luck hope this helps.
Bob U.K
June 2016