Thetford C500 Toilet - Red Flashing Light...🚨

[March Hare]

Sorry in advance for this toilet thread!

We've got a Thetford C500 toilet in our Motorhome (Hymer MLT 570).

I replaced the main "Lip Seal" in the cassette yesterday - using a genuine Thetford seal - following the Thetford video on YouTube.

All's fine with the seal, and I made sure that the float arm was moving freely when I put the cassette back together again.

But the light on the control dial beside the toilet is now flashing red. I've removed the cassette and reseated it, and still the red flashing light.

Any suggestions please on how to fix this - it's as though the toilet is not sensing that the cassette is in place?

 

[CV20Bobby]

Maybe the Reed switch that usually indicates cassette full has gone faulty , it’s at the lower back when you look inside the hatch that holds the cassette, it’s held in place with 2 cross head screws. Never had to replace one though so it’s just a suggestion.

Are you sure the cassette is fitting correctly in the hatch ?

Maybe other suggestions from other Funsters will help.

 

[March Hare]

Thanks @CV20B !

I'll certainly look into the switch possibly being broken thanks. Also, I've tried removing and reinserting the cassette, but it doesn't change the ref flashing light unfortunately.

Thanks again!

 

[Jimbohorlicks]

Just pull your cassette out and give your cassette a good shake. You mention you had been freeing up the float arm .there is a magnet in thar that operates the read switch you may have disturbed it.

 

[Howard B]

Our level float was gunged up and sticking. Stripped it out & cleaned it all good now.

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[CV20Bobby]

I would agree , most likely the float switch .

 

[CV20Bobby]

Sorry just realised it’s a C500 cassette you have , the reed switch is on the main pcb ( I have a C260 cassette so it’s different and you remove the cross head screws ) on your it’s far easier to access, here how to replace the pcb ,

 

[March Hare]

Just pull your cassette out and give your cassette a good shake. You mention you had been freeing up the float arm .there is a magnet in thar that operates the read switch you may have disturbed it.

Thanks Jimbohorlicks - When I replaced the new "lip seal", I gave the insides of the cassette and the mechanism a good clean, including the float and float arm. I've also checked that the magnet is still in place in the little compartment besides the float on the float arm.

Our level float was gunged up and sticking. Stripped it out & cleaned it all good now.

Hi Howard B - thanks - I've given the float and float arm component a good clean and it's not snagged - and moves freely.

I would agree , most likely the float switch .

Yes, that's what OH thinks - he thinks it's too much of a coincidence that when I replaced the seal, that it fixed one problem, but created another - so the flashing red light must be linked to me replacing the seal.... I guess at least I've fixed the leaking cassette!

Sorry just realised it’s a C500 cassette you have , the reed switch is on the main pcb ( I have a C260 cassette so it’s different and you remove the cross head screws ) on your it’s far easier to access, here how to replace the pcb ,

Thanks very much CV20Bobby - the video was really helpful, and having googled it, I now I know (a) what a "reed switch" is, and (b) where it is located on the C500! Every day is a learning day!

Anyway, I've used a magnet to test the reed switch, and when I move the magnet in front of the PCB, the light beside the toilet turns from flashing red light to solid red light.

I'm not sure what this tells me - does this point to the cassette or the PCB? My next thing to try is to completely disassemble the cassette (again) and carefully put it all back together, just in case I've missed something....

Any other suggestions would be very gratefully received!

 

[CV20Bobby]

I would think the Reed switch is operating if it goes solid red. Have you tried filling up the cassette ( with water ) and putting it into the cassette hatch , if the float switch is operating ok then the solid red light should show . ( the float will be at its highest point and should show a solid red to indicate cassette full ) If that doesn’t work maybe the float magnet is not close enough to the reed switch? If you are 100% sure the magnet is still there . Does it stop flashing when the cassette is out ? If none of that works I am guessing maybe the main pcb is faulty but that’s a guess. Have you tried flushing the toilet a few times another possible source of fault could be the flush operating button .

 

[March Hare]

I would think the Reed switch is operating if it goes solid red. Have you tried filling up the cassette ( with water ) and putting it into the cassette hatch , if the float switch is operating ok then the solid red light should show . ( the float will be at its highest point and should show a solid red to indicate cassette full ) If that doesn’t work maybe the float magnet is not close enough to the reed switch? If you are 100% sure the magnet is still there . Does it stop flashing when the cassette is out ? If none of that works I am guessing maybe the main pcb is faulty but that’s a guess. Have you tried flushing the toilet a few times another possible source of fault could be the flush operating button .

Thanks very much CV20Bobby

I'm pleased to say I've got a positive update. I completely dismantled the cassette mechanism this afternoon, removing all the screws and separating all the components, gave it all a more thorough clean and put it all back together (I was pleased I'd taken a few photos!).

Anyway, I've just put the cassette back in, and hey presto it works now, just the green light!

I'm really pleased that it's working now, but I wish I knew what I'd done!

Thanks for everyone's help and suggestions!

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[CV20Bobby]

Glad to hear it’s sorted , you do know you are now officially the Thetford C500 go to expert