# Thetford C250 internal wiring?



## Agilityman (Aug 17, 2009)

I have a 2011 Chausson Flash S2. Several reviews have mentioned how badly placed, the flush button is. However there is really no where else the flush button with its oversize bezel can go. 

I want to position a separate push switch (18mm square) that will operate in parallel with the existing flush button. Does anyone know which wires I splice into? There are 8 wires to the flush buttom assembly! 2 of which are connected to the solenoid valve for the flush as my van has a pressurised water system. I get 12v across these two when I press the flush button.

Any help would be appreciated.


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## erneboy (Feb 8, 2007)

Due to a recent mishap my C250 stopped working. Being in Spain I didn't fancy my chances of getting parts. 

I just spliced into the two wires going to the solenoid you describe and fitted a push button out of the way under the counter top in the bathroom (much easier to use now). All is fine except that the red light for telling me it's full doesn't work anymore. That's no big loss to me, anyway yousr may still work. It took about half an hour to do the wiring and I had to drill two small holes (well hidden in cupboards) to bring the wires in. Hope that helps.

By the way tell your family not to pee into the locker when the cassette is out for emptying, Alan.

Edit: That's not quite right, I just put the switch in the live/brown and left the blue as it was.


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## Agilityman (Aug 17, 2009)

Thanks for trying Erneboy.

However, with my unit the two wires going to the solenoid are only 'live' (showing 12 volts on my multimeter) when the original Thetford push button is pressed. So I cannot see how putting a switch between them can operate the solenoid? Can you see my point?


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## erneboy (Feb 8, 2007)

Yes, you are right.

Here is what I posted at the time http://www.motorhomefacts.com/ftopic-102659-days0-orderasc-0.html

The last post gives my solution although not very clearly I now see. What I think I did was to find another live and splice into that via my switch and back to the brown going to the solenoid. I am afraid I don't really remember. It is a quick, easy job requiring just a little thought, Alan.


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## kandsservices (Sep 5, 2010)

Youre van is still under warranty and i would advise against modifiying any wirng to your toilet system as it will probably invalidate your warranty
kev


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## Agilityman (Aug 17, 2009)

Thanks Erneboy, that makes more sense. Will set out tomorrow to do more tests and try out what you did.

kandsservices - sorry, but life is for living, not worrying about warranties to be dealt with by a dealer who couldn't care less (believe me, I wouldn't trust my dealer with any warrantry claim). I am not going to live with an awkwardly placed flush button for one or two years, just in case I need to make a warranty claim. If something goes wrong with my thetford toilet that has nothing to do with the electrics - I expect the warranty to be honoured!


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## erneboy (Feb 8, 2007)

No disrespect to Kev and I do understand what he is saying but the changes would not be noticed unless someone was dismantling the toilet electrics and that won't happen unless you take it to them with a problem.The switch on mine is tucked away under the bathroom work top. It's easy to reach without having to bend down but can't be seen and won't be found by accident, Alan.


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## ICDSUN (Oct 10, 2006)

This may help
http://www.thetford-europe.com/web/...50_installation_instructions_42654_100909.pdf

Page 32

Probably just the 12v + feed being switched will achieve what you want

Chris


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## Agilityman (Aug 17, 2009)

Sorry ICDSUN, that doesn't help. The Thetford instructions only show the external wiring,e.g. how to connect the 12v and earth only.

I've taken the unit apart and worked out the circuit diagram. You actually need to switch an earth wire to one side of the solenoid. To just switch a solenoid on and off, there are 3 diodes and 1 MOSFET (Metal Oxide on Silicon Field Effect Transistor).

If anyone would like a copy of the circuit, just pm me with you email address and I'll send you a 'Word' document with the circuit diagram.


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## rayc (Jun 3, 2008)

Agilityman said:


> Sorry ICDSUN, that doesn't help. The Thetford instructions only show the external wiring,e.g. how to connect the 12v and earth only.
> 
> I've taken the unit apart and worked out the circuit diagram. You actually need to switch an earth wire to one side of the solenoid. To just switch a solenoid on and off, there are 3 diodes and 1 MOSFET (Metal Oxide on Silicon Field Effect Transistor).
> 
> If anyone would like a copy of the circuit, just pm me with you email address and I'll send you a 'Word' document with the circuit diagram.


Interesting but can you confirm that the standard switch is push to close the contacts which feeds 0v, [earth wire? in your explanation], to operate the solenoid. Can you attach your word document to your reply? Ray


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## erneboy (Feb 8, 2007)

I don't have the electrical know how to figure all that out. I just found a live and switched it. It works fine now but I will fix it properly when I go home. I need the little printed circuit board which fits in the rear of the locker, Alan.


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## Agilityman (Aug 17, 2009)

Erneboy & rayc,

If you send me a pm with your email address I will gladly send you a word doc. with the wiring diagram.

Not sure how I stand if I publish it on the forum?

The push switch is a push to close and it does switch the 0volts.


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## rayc (Jun 3, 2008)

Agilityman said:


> Erneboy & rayc,
> 
> If you send me a pm with your email address I will gladly send you a word doc. with the wiring diagram.
> 
> ...


Then why can't you simply connect a remote switch in parallel with it? Pressing either switch will operate the solenoid.


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## Agilityman (Aug 17, 2009)

rayc,

We appear to be at cross-terms here. The new switch is effectively wired in parallel - however you can't get directly to the original push switch terminations. The original push switch is a SMD tactile switch i.e. it is a Surface Mounted Device on a printed circuit board which has been 'flow soldered'. You need to know where it is effectively wired 'off' the printed circuit board.


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## erneboy (Feb 8, 2007)

Thanks for the email Agilityman, Alan.


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