Thetford C250 Warning Light

[Urban Spaceman]

Hi,
I'm new to the forum and would like some help.
I have acquired a 2011 Swift conqueror with a Thetford C250 cassette toilet.
The problem is the red warning light did not illuminate . I read up about it and cam to the conclusion the the float/ magnet must be stuck.
As it was getting on a bit I bought a refresh kit for it comprising new tank seat and cover.
The result is the warning light is on whether the tank is full or empty.
So then I fitted a new p.c.b. , the lower one in the compartment with a single reed switch.
No change light still on.
Any Ideas?

Cheers
Urban spaceman

 

[littlebasher]

Is it lit with the cassette removed?

If so, and you changed the reed switch PCB, only really leaves the main PCB

 

[Woodentop]

The float is in the end of the case and is only seated in a pair of curved hooks. If it gets out of alignment - or gets clogged up with bog paper - it will not move.
Get a piece of timber about 15in long - 2x2 or 3x2 is a good size. Extract the cassette, remove the top slide, place the wood in the slide shoulders and turn the assembly about 1/8 turn anticlockwise (there are alignment marks on both the case and the trap assembly.) Lift the trap assembly out and you will be able to see the float on the back wall of the cassette - the cause will be obvious if the float is a fault.
When re-assembling it is a good idea to to wipe all the seals around the trap clean - remember the actual trap seal is like a bellows so can catch material - then run a wipe of a good quality olive oil around the rubbers with your finger (in a vinyl glove of course!) to lubricate them. If the trap assembly is caked in crud (calcium carbonate) put the whole thing in a bucket of warm water and vinegar overnight, then spray the sliding parts and tracks with something like GT85 (note <NOT> WD40!) to help it move easily.

 

[Urban Spaceman]

Thank you littlebasher and woodentop.
Yes the light was on with the cassette removed.
I had another look at it today. Took the new pcb out and tried to push it in more firmly and managed to snap off the reed switch.
Took the board into my garage and re-soldered the rs onto the board.
Tested it with a magnet and it worked.
Put it back into the van and Hey Presto it worked, no light on.
Filled the cassette up with water and the light came on.
drained it and light went out. I think it must have been a dry joint or something on the pcb.
The cassette is brand new a so I doubt if the magnet/float had come unhooked without even being properly christened but then again there must have been a fault on the new pcb!

Cheers

 

[Hutch]

US, glad you have the problem solved, Our light failed to come on about 6 years ago, a look in the honey bucket tells you when it needs emptying.
Well done.

 

[Woodentop]

The atmosphere inside the (otherwise) non-ventilated waste container housing can cause significant corrosion to soldered joints. On our last van - a Pegasus 462 - I had exactly the same problem. Took the board out, cleaned the contacts with a fibreglass brush, resoldered the reed, and wiped a smear of Waxoyl across the whole board and some Electrolube on the contacts - never had another problem with it.

 

[Urban Spaceman]

Yes looking in the bucket is the best way. My thing is, I hate gadgets and mechanical bits not working as they should on the caravan or my cars, even if I never use them!
Waxoyl sounds like a good idea Woodentop like you say not an ideal environment for electronics!
Cheers All