Old Topic but searching for an answer for Black monitor

[Tobster]

Hi all! I know black tank and grey tank monitors are notoriously prone to fail, ,and I have seen many post about black tanks always showing a level of fullness. Mine continually shows Empty!! I have used every method I can find to clean the tanks and I do believe they are as clean as I can get them. I just need an explanation of how the sensors are wired and if all the sensors need continuity thru them to show full?....I am guessing that since it shows empty I do have voltage there!

Thank You
Tobster

[Grumpy]

Sounds like a bad ground or loose wire at the panel.

[vwnut]

Some information here.
Scroll through the pics; there is a wiring diagram.

https://www.classacustoms.com/KIB-3-...ate_p_472.html

https://www.dutchmenowners.org/forum...0&d=1464375899

[JimD]

These things work by sensing continuity between the lowest sensor and the other 3 sensors above it. The liquid inside the tank will touch the lowest sensor stud and then as the level increases, the "water" will hit the next sensor up in the tank. This completes the circuit causing an LED to come on.

The bottom sensor is the common link to all sensor operation. If it fails, no LEDs will come on. If any other sensor fails only one LED will fail to operate. These "sensors" are basically just a bolt through the side of the tank. The metal in the bolt makes contact with the liquid. Nothing magic here.

I would check the wire connection on the bottom sensor. If it looks good, jumper the bottom sensor to any other sensor and see if the LED comes on. If jumpering it causes it to come on, maybe there is crud on the bottom sensor preventing it from touching the liquid.

If jumpering it doesn't cause the LED to come on, there may be an open between the tank and the display panel. I would first reseat the connectors on the display to see if that solves your problem. The display may also be bad. If you can determine which wires are the sensor ones at the display, you could jump them there.

[Tobster]

You all are a wealth of information!

Tobster

[us71na]

Be sure to look under your trailer. The wires for my sensors were hanging down where any rod debris could easily snag one of the wires and rip them loose. I used a bunch of zip ties to run them up out of harms way.

[JFlightRisk]

All the above info is spot on. If your TT is open underneath to see the tanks and wires, a 2 foot length of any small gauge wire and an assistant inside to watch the monitor will help.

Crawl underneath and touch one end of your wire to the sensor with the white wire (the common, or ground), and the other end to the other sensors (yellow, green, and red or orange) one at a time, and have the inside person tell you which LEDs are lit, if any. I used a length of bare telephone wire. You can't get a shock from it. This is how I tested the new Horst sensors I installed in the gray tank, and found the Full and 2/3 wires switched from the factory.

[2021JayFlight28BHS]

Agreed, recently had to drop my underbelly and the nonsense wiring they have on my sensors I’m surprised they even work…. Prob good idea to check that all out…. If like mine they have a wire nut connecting 2 wires which would prob be ok if the thing never rolled down the highway…. But I’m sure it will fail at some point because of that.