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Cassette toilet repair?

Although I've been very happy and had many years trouble free with your caravan toilet model C2 bench cassette, there's now an intermittent problem that I hope you can offer some assistance with.

Both the flush (push down) and rinse (twist) functions only operate intermittently. Do you have any suggestions on the possible cause?

I suspect the two switches (item 57 on your diagram) may be at fault, but are there any other wearing parts that may be causing this issue?

If you agree item 57 is a possible cause, is it possible to change while the unit is installed in the caravan, or does the entire unit need to be removed to access the switches.

Thank you in advance for your assistance with this matter.

Best Regards

December 2012
Firstly who are you addressing this is not Thetford site going by C2 bench type I have had 3 caravans with same type electric pump.

Now the operating knob is pressed for flush and the twist or turn is to open or close the blade in the bowl. Both actions independant of each other now pump intermitancy could be the micro switches or even the pump itself.
Try this before switches as that's not and easy job.
Remove the toilet roll holder on the bench and lift out the cup it sat in (push fit no screws) If not discovered already that is the access to pump. The large tube is the flush tube push fit both on pump and bowl side. The pump is in a plastic cage secured by one domehead cross head screw undo the screw lift out pump and cage. Turn the pump over on the base you can insert a thin screwdriver or similar to gently turn the impeller blade keep turning until you feel it turns easy replace the pump in a bowl, bucket or saucepan of water and test pump action (these pumps must not be run out of water it can damage them).
What it may be is lime build up on the impeller shaft so slowing or causing intermittent operation.
the other thing to look for is bad electric connection in the 12volt run to the micro switches. Renew switches as a last resort. see below just found it on disc.

PAGE 1 OF 3 for Thetfords C2 bench toilet, not moder swivel ones.
see page 3 on Thetford access at end of this info.
GOOD LUCK! from Lunar owner.

Note: Compiled because Thetford do not cover possible jammed pumps or other faults like block terminals going ‘manky’ and arresting current.
As for micro switches supplied by another camper who gave permission to add what he sent me after he contacted me about his pump.

If you are not clear on what to do then e-mail me again.

If you know there is current to the pump go to ‘To access the pump’
An easy test to find out if current is reaching the pump carry out the following..
power up your 12 volt system.
Turn on the 12volt toilet cubicle light or if there isn’t one, one in the saloon area you can see [one over the sink/hob if there is one will do if like mine opposite toilet].
Press the toilet flush and take note if the light dims then goes back to normal on releasing the flush button. If it does it proves power is reaching the pump but the pump impeller is either jammed or the pump is knackered. Or use a multi meter.
If no current at all check the fuse in the holding tank housing, to the left I think.

Once in to tank check the flush tube is connected to both the pump and the side of the toilet. If yes carry on to remove pump then pull flush tube off pump, or just pull it off if you need more room to remove pump..

To access the pump remove the toilet roll holder. PULL up on the holder housing this, it’s a push fit giving access to the water tank. It may need easing around the edges. Vaseline edges before replacing when repair completed to make further removal easy.

You will see the pump flush tube follow down in to tank and there is the pump in a cage held by one screw undo screw lift cage and pump from tank.

To free the impeller on jammed pump remove the pump as above turn it upside down and with small screwdriver turn the impeller about three turns until it feels to be running free . Don’t fix pump back in position just drop it in water, either in the tank or a bucket of water as long as It’s submerged [submersibles need to be wet, running dry damages them]. Oh! make sure the flush tube is still connected or you’ll get wet. If it works job done.

Cut away the existing pump about six inches or 150mm up the cable from the pump and note one wire has a tracer [secondary colour] in the wire the secondary wire on new pump must be connected together don’t connect a plain single colour to a wire Pwith a tracer colour. Fit on each of the wires one of the heat shrink joints then twist
Page 1 continued. so it doesn’t go into four pages)
the wires together. One with tracer [Secondary colour] to the new pump wire with secondary colour. Then connect the two single colour wires together. Slide the shring joints over the joints and heat shrink them down. Then wrap tape around ends of shrink joints to ensure seal. Stow the joint section on the shelf at back of tank so it’s out of the water.

SHRINK JOINTS. [search internet for supplier if local shops don’t stock.]

You can purchase from car spares small shrink wrap sleeves heat sealed for the wire joints just remember to fit them on the cable before connecting wires together. Simply slide sleeves over joined wires and follow heat application instructions.
You could add some water proof tape after to be sure.

Re fit flush tube to new pump and test using a bucket of water to submerse the pump. Remember don’t test any pump dry it will damage them.

From another forum reader haven’t got his mail address.

volt drop can be a bitch to trace. could be a dirty / bad connection or switch. what ya need to do is test the cables with a low reading ohm meter. should get very low reading ie 0.5 ohms. (obviously with the switch in closed position) another way to test is to get some cable, run it from battery direct to pump (a similar length to what's installed) if the problem is still there the battery needs fully charging (even new ones can be down on power without a good solid charge up) if the pump works ok with temp wiring ya need to check voltage going into the first switch and then coming out, same with 2nd switch if 12v in and 12v out. this will tell if the switch contacts are dirty. *To see if the battery is fully charged or not, switch on a couple of lights and test voltage at battery terminals, should still give at 11v. with nothing switched on at all you should get at 13.2 volts. (6 cells at 2,2v /cell)
if everything checks out, ie battery good, 12v out of switches, then the negative from the pump to battery is suspect. again, can be checked with temp wire from battery to pump.

ADDENDUM: Pump repair/replace look also for a bad joint in cable if current drops or not showing and fuse is ok.

Addition with permission from another camper

• I assume he means the flush turn knob can be removed this way once screws out of cover/s

Hi Bob, many thanks for your very quick return e'mail, which is a great help, with the toilet out, I have been able to test all switches, but I am going to replace them, as its very easy whilst toilet holding tank is out, I can tell you, that the only way to replace switches is not through the turn handle, if you open toilet door and swing out flush filler unit, then remove blanking plate,
• ( just held in by push pop ), you will see a long grey cover held in by 4 screw and one up inside the other twist unit with micro switch attached , pull out this unit, and the long grey cover will drop down with the other micro switch inside it, pull apart cable connecters and *the cover unit can be removed from inside the toilet and very easly replace switches, put back in reverse order, hope this helps, for Australian campers.

Access no matter which for info.
on home page click on ‘Service’
next page click on repair instructions
next page click on sanitation. ( worth doing fridge also)
down load pdf the repair instructions covers all look up what referes to yours.
Go back a page and down load in turn all you think you might ne

Bob UK
December 2012


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