Could be the pump has jamed.
send email to robertwhiting76(at)hotmail.com change (at) to normal email abreviation and don't include the brackets or it won't go. can't put email in forum it wont take it. So many posted similar problems I've created a file on the C2.
Meanwhile Thetford do pdf repair downloads [pump jaming not included] follow :>
UK www.thetford-europe.com
Australia www.thetford.com.au
Australia site has stockist list.
HOME PAGE SELECT ENGLISH {if in Australia forget this selection
NEXT PAGE SELECT CUSTOMER SERVICE (tope line)
NEXT PAGE SELECT USER INFORMATION (left of pic)
NEXT PAGE SELECT REPAIR INSTRUCTIONS (left of pic)
NEXT PAGE SELECT BUILT IN TOILETS [top right of pic]
NEXT PAGE SELECT C2, C3., C4 or select your model range
NEXT PAGE PDF Files YOU ARE NOW IN PDF FILE LIST
bob, May 2009