# Stiff Thetford Cassette Blade !!



## namder (Sep 20, 2006)

I've searched the forums to no avail.

The blade opener became stiff and needed two hands to operate and then only opened to half way. At this point I noticed that the seal had gone wrinkly and leaked when carrying upright. I replaced the seal and lo and behold the blade became much easier to operate and also opened fully. However during our first weekend away after fitting the seal, the blade became increasingly tighter until it ceased to open at all. Tried olive oil on the seal which now allows it to open but it's stiff and only opens half way again.

Anyone any ideas.

Thanks in anticipation.
NAMDER


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## muggers (Jul 14, 2007)

Keeping this bumped until someone who knows can answer... How old is your system? Shouldn't happen with a new seal I'd have thought. Hmmmmmmm


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## namder (Sep 20, 2006)

Motorhome is 15 years old and assume the cassette is the same age.

Namder


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## wobby (May 1, 2005)

Try taking the cassette out and seeing if the blade will operate if not then you know the problem isn't the Cassette. If yes the a closer inspection of the cassette may determine the problem, is something miss alining or catching. 
Wobby


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## annetony (May 1, 2005)

We replaced our cassette as it was leaking, we had noticed it starting to be quite stiff to open, the new one is fine easy open with no stiffness, quite costly though if you can just replace blade & seals

Anne


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## mangothemadmonk (Aug 6, 2006)

Try here

Hope that helps.

Johnny F


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## namder (Sep 20, 2006)

Unfortunately that thread only deals with replacing the seal which I have already done.

The problem seems to be in the cassette itself. Outside of the housing the cassette mechanism seems a bit stiff and with the cassette removed the inside control moves quite freely.

Namder


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## ingram (May 12, 2005)

This might not be of much help but mine is stiff too, although it usually opens about 95% of the way so is not so much of a problem. I suspect that the mechanism is fitted bofore the two halves of the cassette are 'welded' together.

You may find something on the Thetford website: maintenance tips etc. which will help you to understand what is inside it.

Harvey


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## vmeldrew (May 3, 2007)

I had this problem in my last MH and had rubbed olive oil around the seal to no great effect. I was then advised to pour olive oil on to the plate to cover the seal and let it stay there for a while and this solved the problem.


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## namder (Sep 20, 2006)

[/quote] had this problem in my last MH and had rubbed olive oil around the seal to no great effect. I was then advised to pour olive oil on to the plate to cover the seal and let it stay there for a while and this solved the problem.


> Thanks vmeldrew, I'll try that later.
> 
> namder


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## drcotts (Feb 23, 2006)

Hi
Its probally not the waste seal thats causing the problem. Take the cassette out and look at the knob that opens the blade. If you gently prise this up a couple of mm you can then squirt some oil under the knob. Do this and then gob some vaseline uder there also. Now press the knob back down again and you should find its much easier to operate after a few passes back and forth. What happens is the o ring on the shaft under the knob dries out with the formaldehyde in the toiet chemical and makes operation very stiff.

before you put the cassette back in take a look inside the chamber where it came from. When you are in the bathroom and turning the knob there is a shaf attached to the bottom of this handle and on the end of this shaft there is a moulding and micro switches attached. This moulding sits over the knob you just greased. If this moulding is cracked it will only allow the flap to open half way. You need to replace it. It screws off by popping the centre of the turning know off and putting a long pozi/phillips screw down and unscrewing it. make a note of the wiring for the micro switches. (these stop people using the loo with no tank in).

Phill


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## namder (Sep 20, 2006)

> Take the cassette out and look at the knob that opens the blade. If you gently prise this up a couple of mm you can then squirt some oil under the knob


Thanks, that's done the job

Namder


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## Waleem (Nov 1, 2006)

Thanks for the tip-mine was stiff and has freed up nicely. One point-I used nylon lubricant rather than oil. Oil makes rubber seals swell and decompose over time.


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## ingram (May 12, 2005)

drcotts said:


> Hi
> Its probally not the waste seal thats causing the problem. Take the cassette out and look at the knob that opens the blade. If you gently prise this up a couple of mm you can then squirt some oil under the knob.
> Phill


Excellent! While emptying etc. my cassette today I tried to remove that knob to have a look. Can you prise it up and remove it altogether for a good look inside? I assume that it just pushes on.... don't want to break anything.

I'll have another go tomorrow.

Harvey


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## drcotts (Feb 23, 2006)

ingram said:


> drcotts said:
> 
> 
> > Hi
> ...


Hi harvey
I wouldnt try removing it if i were you. I dont know whats under there but i expect its a moulding or linkage inside the tank thats snapped on during assembly.
I would just lift up slightly and spray nylon lubricant or similar. It can probally be removed but i wouldnt try unless i had to.

Glad it worked for you all. You think i spend time messing about in the loo i bet.

Phill


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## LeoK (Apr 21, 2006)

Hi folks..

I believe that the 'approved' lubricant is Silicone Oil - such as Cara-Sil (which is also very good for other seals around doors and hatches - including the car doors).

There could be a limescale type build up within the tank, affecting the blade mechanism inside. I bought some Citric Acid Crystals (available from cooking supply shops or pharmacist) to use for descaling. Has a side effect of leaving the container smelling clean as well.

I left the Citric mix in for twenty four hours, rotating the tank so that all surfaces got a good soak. Upside down overnight, which was the longest break.

A useful read about Thetford cassettes is at this page.

Information on the Thetford Toilet, and handbook in PDF format, can be found at their web site: www.thetford-europe.com/


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## ingram (May 12, 2005)

LeoK said:


> A useful read about Thetford cassettes is at this page.
> 
> Information on the Thetford Toilet, and handbook in PDF format, can be found at their web site: www.thetford-europe.com/


Yes, repair and maintenance procedures in pdf are downloadable from there: I just remembered that I have some downloaded already: no mention of removing that blade knob but some have a replaceable blade it seems. Important to make sure you have the pdf for the correct model and age of toilet; quite a few variations.

Harvey


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