flush wont work in my thetford cassette c-402c?

A point to remember is place the camping type toilet questons in Caravan/Motorhome section not the plumbing section. You will get more replies. Add same question you may get someone with same toilet who's cured the problem.
Meanwhile back at the problem.......
www.thetford.com contact them and you may be lucky and they MAY tell you what could be wrong. Don't hold your breath.
Check if it's the pump by turning on the 12volt lights in the toilet. Press the flush switch and take note does the light dim when you press the switch. Yes! then the pumps jamed. Any way if you know how to get to the pump remove it look at the base and if you can see the impelar turn it carefully with a small screw driver until it runs free. If the light doesn't dim it could be the switch.

If you've no user manual then Thetford do downloads.
entering the thetford site click on products. Select permanent toilets, Select the 2nd one middle row [your toilet] click on the toilet info line and a download screen pops up select either open or save to your files. Go back and do the same except select Parts this time and down load the parts list with pictures its handy if you need parts you can show them what part.

Nobby
July 2008