Thetford C4 Cassette "Blade"

Jeff d

Active Member
Jun 5, 2012
302
2006 Fleetwood E2.

From what I've gathered I have the C4 potty. Also the previous owner put blue chemical in the fresh water tank. Everything still seems to work but I will be flushing out the fresh water tank asap.

When I first pulled things apart the "blade" (Round black disk that "closes" the tank), as it seems to be referred, to as had fallen off and was in the bottom of the cassette. So, when it was in the closed position I just would see the arm with the hole in it. I fished the blade out and put it back into what appeared to be the proper position. It seems to work fine but there's really no sealing action by the blade. i.e. if I flush it with the blade closed the water still goes past it into the tank. Should there be a better seal there? There is the rubber seal that seals the potty to the tank but I was thinking that the blade should probably seal up better to keep odors in.

I found a parts diagram for the toilet but it doesn't cover the blade itself inside the cassette. Am I missing a gasket or something?

Thanks,
Jeff
 

Jeff d

Active Member
Jun 5, 2012
302
So, during the process of getting the blue chemical out of the fresh water side, the blade fell off again.

I pulled it apart again and it just doesn't return all the way to the middle. It's about 3/16 off center when "closed".

I found this:
http://www.around-oz.com/innovations_mh/thetford_blade_mods.htm

It's pretty much the problem I'm having but I also think my little "nub" on the bottom of the blade is worn down more than the one in the pic:
thetford_00218.jpg


So, that would keep it from being pushed all the way up against the seal I guess. I still haven't quite figured out how the mechanism is supposed to work nor do I understand why the supposed fix that guy shows with the bolt on the arm would actually help.

I also found this somewhat incomplete drawing/parts list for the cassette:
http://www.leisureshopdirect.com/pdf/c2-c3-c4_holdingtank.pdf

I guess they just don't sell the parts that aren't identified at the bottom

I'm thinking my whole blade rotating assembly may be off by a couple of degrees. I've watched it work in a mirror and everything appears to do what it's supposed to do but it just finishes about 3/16" too soon.

The blades seem to only be available from some European vendors.

I found this too:
http://www.thetford-europe.com/en/products/toilets/cassette-toilets/~/media/Files/Thetford/Service%20documentation/Repair%20instructions/Sanitation%20Repair%20instructions.ashx

Covers a lot of repairs for different Thetford potty related issues but not the one I have.
 

campfreak

Super Active Member
Jan 13, 2011
2,025
I had the same problem. I don't really understand the repair in the pictures, either. I ended up making a new blade from a flat piece of ABS plastic ant a short piece of 3/8 dia ABS rod. Works great once you get the length of rod correct. Now there is a flathead screw visible when I look in the bowl, but I can live with that.

Greg
 

Blkvoodoo

Active Member
Aug 21, 2011
524
Have you tried Thetford USA ?

I emailed Thetford USA ( AnnArbor Michigan ), and was given this phone number for the Consumer Line, 800-543-1219.

They may be able to help
 

Jeff d

Active Member
Jun 5, 2012
302
campfreak said:
I ended up making a new blade from a flat piece of ABS plastic ant a short piece of 3/8 dia ABS rod. Works great once you get the length of rod correct. Now there is a flathead screw visible when I look in the bowl, but I can live with that.

Where do you get flat pieces of ABS and rods?

Did you have the issue of the blade not being perfectly centered in the opening too?
 

Jeff d

Active Member
Jun 5, 2012
302
Blkvoodoo said:
Have you tried Thetford USA ?

I emailed Thetford USA ( AnnArbor Michigan ), and was given this phone number for the Consumer Line, 800-543-1219.

They may be able to help

I'm going to give them a shot next week but from what I read everywhere else last night, they're extremely unhelpful.

Looks like worst case I can get a new cassette from a UK vendor for about $130 US + shipping. Hopefully I can avoid that.

It seems like if I could put a stainless steel thumbtack (If there was such a thing) in the protrusion on the blade I could make up for the worn off plastic.
 

Blkvoodoo

Active Member
Aug 21, 2011
524
Maybe I got lucky, or what I was looking for was an easy find. though I did have the part numbers of what I needed.

my only issue was the cost of the parts for what they were, but specialized items tend to be that way. ( was still half what an RV retailer wanted )
 

campfreak

Super Active Member
Jan 13, 2011
2,025
Jeff d said:
Where do you get flat pieces of ABS and rods?

Did you have the issue of the blade not being perfectly centered in the opening too?

Yep, same exact problem. Blade would not seal, kept falling out. I think I did find the actual part number for the blade, but I think it would have come all the way from England, and I had a trip coming up, so I just fabbed a replacement . I work in a machine shop that does a lot of plastic stuff, so we have a lot of ABS laying around.
 

Jeff d

Active Member
Jun 5, 2012
302
I contacted Leisureshopdirect and this is the response I got:
Unfortunately we no longer ship orders over to the United States of America. This is because we experienced several problems in the past.

Sorry we could not be of help to you at this time.
 

Jeff d

Active Member
Jun 5, 2012
302
I'm going to contact Thetford US today with the part numbers I got from Leisureshodirect and see if there's any way I can order those parts from them. I can't believe that they wouldn't sell a wear/maintenance part through US dealers.
 

Jeff d

Active Member
Jun 5, 2012
302
Thetford US says that the blade is discontinued. They could only sell me a whole cassette for $168.83 (I assume + shipping).

Has anyone replaced the blade arm in one of these? Oddly, Thetford would sell me the blade arm for $80. Looking at that stuff in the mirror and the exploded view I assumed that everything would fly apart if I removed that screw that everything pivots around. The guy on the phone says it can be replaced through the hole.

I'm definitely not interested in paying $80 for a flimsy piece of plastic but I might try to make one out of aluminum or SS. Then make a new blade out of a sheet of plastic. Just cut a circle with the router and then use a bolt with an acorn nut to ride on the other plastic piece.
 

EV2

Active Member
Mar 18, 2008
462
Thetford in the US is a rip off. As per the thread referenced above the blade is available in Europe where the item is manufactured. The blade being discontinued is code for Thetford not offering them here. Apparently Thetford in the US has figured out this is the way to rip people off. The replacement blades have been redesigned but the assembly that I received in the US still uses the older poor design that is guaranteed to fail. Use the link offered above and order an improved blade from Europe. It is an updated design and you don't reward Thetford by paying 10 times the actual cost for them to use up their junk old stock assemblies. It takes only minutes to install and you don't even need tools. As a result of this treatment by Thetford-US I will never own another one of their products – ever.
 

BelchFire

I speak fluent vise-grip
Mar 29, 2012
1,704
SE Georgia
I see an opportunity here! How has a "good" blade that they could loan me long enough to take some measurements off of?
 

Jeff d

Active Member
Jun 5, 2012
302
So, upon further analysis of the design I think I understand how this happens.

First the blade arm fit becomes sloppy in the channel on the blade opener (The other arm below it that raises it up). This then allows the blade arm to travel further (counter clockwise) than it should. This results in the blade being off center by a little bit. So, when it's raised up it gets tilted. Once it starts to tilt it then can fall off the trailing edge of the blade opener in the closed position and get jammed up. then the little nub on the bottom of the blade gets wedged against the blade opener. At that point someone "fixes" it by forcing it to open, breaking off the little nub. From that point on it won't seal properly as the blade isn't lifted high enough due to the lack of a "nub".

So, a new blade would likely fix the sealing problem for the moment but it would be likely to recur, especially with kids using the potty, since the other components are still worn and sloppy. If it's just you using the mechanism then I'd think it could be prevented by being gentle with it + lubricating it frequently. I think a new blade + fabricating some sort of stop, possibly out of aluminum angle iron and pop rivets, would be necessary to prevent the blade arm from being able to rotate past the blade opener. All that prevents it in the current design is another plastic nub on the blade arm that runs in a track on the blade opener.

At this point I've got so many other things to address on this camper I'm inclined to just buy another cassette for the ridiculous $160 price.
 

Jeff d

Active Member
Jun 5, 2012
302
Also, once I either repair or replace this one I will keep a spray bottle of olive oil near the potty so that whenever I dump it I can squirt some on the mechanism to minimize wear and the amount of effort required to open and close it. I think that will add years to the life of the mechanism.
 

bud121156

Western North Carolina
Apr 15, 2007
4,632
North Carolina
Good deal Jeff. That's around what I paid, from the other place in the thread above. Should work out good for you! Have to bookmark this place.
 




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