I thought I’d share this with everyone in case they have a similar issue.

After a fortnight in Devon with no issues in our Troll (Ruby) we drove back to Shropshire. At some point we hit a bad pothole and the caravan bounced quite hard. I’m not sure if this started the problem, but anyway when I cleaned the caravan uot a few days after our return I noticed the toilet wasn’t flushing. I did the usual things such as checking the fuses (The toilet is on the same board fuse as the toilet taps, so if they work it’s not the main fuse). I used my multi meter and checked the blade fuse in the waste cassette holder. If you take the waste container out, the fuse is on the left side about 6” in. It is mounted on the side of the reed switch holder. This fuse was OK, so I then took the control panel out and checked the voltage at that.

To get to the control panel you pull the flush handle up and off. Then, gently using your fingers lift the control panel up being careful of the lug at the opposite end to the handle. Turning the panel over, you will see two connectors, one with two black wires (this is from the reed switch in the waste compartment), the other has four wires, a red and black pair and a blue and brown pair. Using the voltmeter set to DC carefully put the probes on the red/black pair. You should see 12v. If you are able place the probes on the blue brown pair and press the flush button. If it is working, you would see 12v across those wires, but in my case there was nothing.

I assumed the control panel had failed, so I spend just under £50 and replaced it. Hmmm, it still didn’t work - very annoying.

My next step was to carefully remove the reed switch circuit board. I extracted the reed switch panel and unplugged the connector. I had to remove some hot melt glue that held the circuit board in place, but once done I applied the multimeter (set to continuity) to the connector on the circuit board. It bleeped constantly, so I applied a magnet to the reed switch (the long component on the inside of the board). After moving the magnet close to and then removing it a few times the reed switch started operating correctly. Near the magnet - bleep, magnet removed - no bleep. I did this several times to make sure it was working consistently. I then reassembled the circuit board in the holder (a dab of hot melt glue on the two lugs will hold it firmly in place), then reconnected the connector and put the fuse back in. (Incidentally, the fuse is NOT part of the reed circuit in any way, it is the fuse for the toilet control panel)
I then plugged the control board back together and tested it, and it worked perfectly. I then reassembled the various parts and tested again.

The moral of this is, test everything where you can without making assumptions and wasting £50!!

Yes, fault finding can be an art sometimes: many a time I've jumped to a wrong (and oftentimes expensive) solution

"At least I'll have a spare to hand" I think but funnily enough theres never a problem again:)