The level indicator has stopped working - I've changed the magnet in the cassette but the indicator still doesn't move - it looks a very simple device but very difficult to get at.
Have you tried contact with thetford ?
www.thetford.com click on contact us, it's faint and on the main heading line to the right. Scroll down for the email form.
You may be lucky but don't hold your breath.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix caravans/motorhomes.