Well how things can come back to haunt you so easily
Following my post a few days ago about the perfect operation of our Thetford flush pump, we went away for the weekend in the motorhome, the first trip since Easter. Thetford flush pump wouldn't go. Checked the obvious and found the fuse blown. Replaced fuse, blew again. So the process of elimination began and of course I'd left my multi meter at home (it lives
in the motorhome)
After I'd checked the power feed and microswitch I finally got into the pump and sure enough, the impeller was seized. With a bit of gentle persuasion from a fine bladed screwdriver got it moving again and all is good.
While in the flush tank I also noted the brown slime on several surfaces mentioned by others, although I don't think this was blocking my pump as it happily discharged it into the bowl later - it seemed more like corrosion or perhaps a bit of solid debris (pumice?) binding it, rather than a soft material. Perhaps a caution to be careful in sourcing water for the flush tank. In the past I'd got it from streams and lakes to avoid using tank water when freedom camping and may have picked up a bit of grit.
The only other thing done differently in the last year was taking part in a user trial of a new toilet treatment product over summer which included a top tank treatment as well as a cassette additive (unknown compounds). I have no evidence that this may have caused this issue, but am happy to now be reverted to our fresh flush water and oxidiser in the cassette.
7m Fuso wide body, 420W solar, 230 A/h batteries, 2kW Eberspacher, 255L 230V Samsung fridge, 400L topbox, 195L fresh, 200L grey, Suzuki Jimny toad with 4.7m OK Prowler fishing kayak, MTBs.