Water, gray and black tank grounding connection

[J&AHtravelers]

My 2019, Mallard M27 interior tank monitoring panel is showing all of the tanks as full. I saw in some other posts that people had similar problems with the tank sensors and it was a bad grounding connection. I do not know where to look to find where the tanks are grounded? Is the ground connection at the tongue of the trailer? Is the connection in the electrical panel inside the trailer? Is the connection behind the underside protection paneling? Please give me an idea of possibly where to look to find the grounding connection location.

 

[marknewbill]

I don't know the exact schematic for the sensor, but my educated guess is the panel provides the ground that travels with the sensor wires to each tank. the ground is probably common at the sensor panel itself, so I would check close to there for a loose wire first. it may even be a defective panel.
Just my thoughts.

 

[danemayer]

I believe the ground is made from the test panel and probably is just joined to the nearest ground wire.

But the gray and black tanks will most often show full all the time because of contaminants on the tank sensors. If your fresh tank doesn't also show full even while empty, that's probably the problem.