Well don Mr Trudgion another good informative videoAfter my pump stopped working on the toilet I checked the main 12v fuse then the fuse under the waste holding tank, then tested the pump all were ok here was my problem, so temperary fix was found.
View: https://www.youtube.com/watch?v=IV1ULlgful0
I’ve read if others who did the same as you. The original design is an absolute nightmare and does no credit to either Thetford or the designers of the caravans who allowed it anywhere near their creations. With a bit more ingenuity you could have made it into something akin to a Gerberit toilet.I have posted this previously so just to jog memories our van is now 10 years old in its early days I had to have a new board fitted the one on top of the flush tank followed by 3 more,the contacts were corroded since then it has had the switch at the back of the holding tank blow and the fuse this has to be the worst idea ever invented. I use a mobile engineer who suggested not necessary for light work as you can see when the tank is full so has taken that stupid board out and put in nice tidy toggle switch . No more boards.
Sir Roger.
Thinking about it how much power does the pump draw, very little I think , would it need a relay for the power.If your toggle switch is a self return one, connect to normally OFF . So when held down the power is on, switch released power OFF.