The C402C Thetford cassette is 3.5 years old and whilst we had a problem with black bits last year, I got rid of them with a weak bleach solution and no longer use a pink flush liquid. However on our last trip, last week, there was no flush and the 3amp blade fuse blew. Replaced the fuse and the reed switch is drawing power but no water flush and no pump sound (there is a tank full of water!). I am happy to remove the pump and clean and check if only I could find and access it. Any ideas? I would be very grateful for any suggestions.