Clearing Black Tank Sensors

JeffroNC

I have flushed and cleaned the black tank in our TAB 400 several times and I can't get the black sensor panel to go to empty. Grey and fresh are working as they should.
My question is: would a wand type flusher down the toilet clean them? If so, where are they located on the tank? Toward the front, driver, passenger, or rear?

Verna

@JeffroNC, I never could get my black tank down to zero on my 400. I do not have an explanation.  

I used the black tank flush, the wand purchased separately, and just a hose gushing down into the tank. I gave up and I just relied on knowing how much was in there, and dumped accordingly. 

JeffroNC

@Verna Thanks, I will cease pummeling the deceased equine beast now. 

m_lewis

When I had the black plastic cover off the bottom installing tank heaters, I noticed the sensors for the fresh and grey water tanks are on the driver side. However, the black tank is not exposed, so I did  not see it.


A frame grab from a video of the factory floor shows a 400 before the walls are attached. The wall side of the black tank is flat and flush with the outside wall, no sensors. My guess is that they are not mounted in the forward side of the tank either, as that side seems to be flush against the bulkhead between it and the Cool Cat. 
Sorry this doesn't help much. Maybe you could rig a mirror on a stick, angled like a dental mirror, put it down the toilet and have a look. If you don't want to do that, I suggest you will find the sensors on the passenger or rear sides. But, if you are pressure washing the tank, why not do the whole thing?

Amazonica

This probably isn't helpful, but I'm in the same boat. I use the Black Tank Flush nearly every time I empty, tried Calgon, Dawn, and even loads of ice/drive around method. I don't put paper in the toilet (takes getting used to, but simplifies things for me).

Best I can get it to is a "Good" (2/3) reading on the See Level, never less even when I know it is completely empty.

4ncar

I can tell you that the sensor is NOT inside the tank, at least not on my 320s.  They are applied as stickers to the exterior of the tank.  I would hunt around the looking for an access panel, which would give you access to it & the wire feed.  This access can be found on the 320s under the sink at floor level, left wall(when facing the sink).  FYI

Sharon_is_SAM

@4ncar - the 400 tank monitors are inside the tank - hence the black tank flush.  The KIB system uses in-tank monitors.  The external tank monitoring system by SeeLevel was changed to the KIB system with the 320 early 2019 models and starting with the advent of the 400.

4ncar

Sharon_is_SAM said:

@4ncar - the 400 tank monitors are inside the tank - hence the black tank flush.  The KIB system uses in-tank monitors.  The external tank monitoring system by SeeLevel was changed to the KIB system with the 320 early 2019 models and starting with the advent of the 400.

Well there it is...🤷🏻‍♂️

DougH

@4ncar I'm with you... kinda glad I have the SeaLevel so we don't have that issue. But experts said too many customers had intermittent tank level reporting issues.

4ncar

@DougH: at least the externals could be serviced/relocated or replaced. I don’t care how clean you get a black tank, I am not sticking my arm inside to remount a sensor!🤢, if that is what has to be done...

JeffroNC

Thanks for the ideas. I do have an 8nspection mirror but it is not that long. I have been wanting one of those cheap borescopes. Maybe I'll pick one up. I promise not to post photos of my findings.   

Mooree

Cleaning the RV holder tank sensors is an essential skill for all motorhome owners. Dirty gray or black radiator sensors can cause odor problems that make you're RVing less enjoyable. Black tanks require a stronger cleaning solution. You can use an enzymatic agent to break down microorganisms and other organic matter in the black-keeping tank. These products contain powerful substances that help break down organic matter and kill microorganisms.

Denny16

We use Happy Camper black tank treatment agent, works well to keep the sensors clean.  Another tank/sensor cleaning trick is to fill about 1/2 with water and add ice cubes/small chunks and take the trailer for a nice ride on a hot so smooth road.  The ice will help clean the tanks sides and sensor with a little gentle abrasive action.
 Cheers 

JeffroNC

Update: I got tired of worrying about the sensors. Now we use the “glug” method. When the tank gets pretty full, the toilet makes a unique sound when flushed. This is followed by “Honey, you need to empty the black tank!”
it works for us anyway, LOL

mjwaldner

The sensor wires come out of the black tank on the front next to the Cool Cat AC under the bench seat on the 2021 T@B 400.