Thetford C-402C not flushing

Aug 22, 2017
Hi- after years of working flawlessly, the Thetford flushing mechanism didn't work on our last trip. The 5 amp fuse in the cassette bay wiring has continuity. All lights, outlets and devices in the trailer worked, but I haven't tested all the fuses in the convertor/breaker box. Before I raise the roof to access the breaker box fuses, does the toilet circuitry come through one of those 12V breakers?

Thank you!


Super Active Member
May 21, 2015
In my Jayco the cassette is powered off of the heater circuit, which also powers the front storage box light.


New Member
May 15, 2020
Did you check for power at the 5 amp fuse. A test light to clipped to ground touching the test point on the fuse on each side of the fuse will confirm continuity and power from the battery, or better yet a multimeter set on 12 or greater DC volts. If there is power there you can look toward the pump. If there is no power you can look toward the fuse panel. Hope this helps.
Aug 22, 2017
Didn't think to put a meter on the fuse socket. Thank you! Just work my way back.

Slow folks like me are a reason for the popupportal, doncha know.


Oct 2, 2015
Lakeland, FL
For ours - 2 things have happened:
1 - the pump motor went bad. Was able to pick it up on Amazon for $40. Easy to install, but the butt connectors supplied in the kit crumbled when crimped and forced a quick trip out to get some more. The Heat shrink tubing has some type of extra sealant in it. There is a 3amp fuse in a holder that is accessed by pulling out the toilet cassette - not just the fuse at the panel. This was blowing before the fuse in the main panel. You have to reach in (at least on our 2716) nearly the full length of the opening to get at it. 1684685971642.png You'll have to remove the handle that opens the toilet for flushing, pry off the outer cover, remove the inner "tray" and then that pump sits down near the bottom - can't see it but you can feel it once you get your hand into the opening. There are several videos on youtube that show replacing that pump. The hose for the water supplied to the bowl in ours would NOT bend very easily - but it isn't clamped on so you can remove it.

2 - The electrical connection that attaches to the circuit board that goes to the pump - doesn't stay attached well, could be the parts we found laying in the "tray" that is under that circuit board. That has caused the toilet not to flush as well. You can see that when you pull up on the handle that opens the toilet for flushing and then pry out the panel containing the button.



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Aug 22, 2017
Well, bless your heart! I didn't know about the second (on mine) fuse. Mine has a 5 amp in an inline socket dangling right at the opening. With your info, I looked again and saw the 3 amp fuse in the side of the housing. It was blown. I replaced it and now I can hear the pump running!

I won't know until our fall trip if there's a pump problem that will cause another failure. But thanks to you, it's hopefully fixed.

Thanks again, Mr. R.