Head Waste Control System Panel SLX250

[Rumour2]

I have an SLX250 with the above panel control and indicator panel (same as on the SLX270). My issue is the indicator should show EMPTY/HALF/FULL, but only shows POWER when I turn the key to on. No indication of the level in the holding tank.
My question is what is the likely issue? The wiring to the panel is intact and I assume with the POWER indicator on, there is electrical source as required.
Can it be a sensor issue on the tank? I haven't tried to check as the access is restricted.
Thanks for any input.

 

[Rumour2]

So, having established that access is a major issue, and reading the horror stories of other boaters on cleaning issues, often with limited success, I find the alternative of external sensors (e.g. capacitive) attractive. Ideally, it would be possible to hook-up the sensors to the existing monitor rather than installing a parallel system ( with all the potential wiring issues). Has anyone successfully done something like this?

 

[Rumour2]

Done some more research on external sensors that may hook up to the existing monitor. One is a set of 3 sensors, example supplier

https://mikroelectron.com/Product/X...id-Level-Sensor-Switch-Signal-Output-DC-5-24V

where each sends a signal at 12v (0v for no liquid sensed). This would align to the 3 wires from the reed sensors of the standard sensors in the tank. The only difference is that the latter just closes the circuit of the 12V LED on the panel back to -ve for each level.

The question now is whether the signal wire from the external sensor is compatible (circuit-wise) to light up the LED, and not blow any fuses. Any experts out there that can comment?

 

[Rumour2]

Here are the wiring diagrams and control panel view. As noted above, the holding tank sensors are not installed, but the diagram shows how it would be hooked up.

 

[Rumour2]

I worked through it and it works perfectly! I actually used the sensor XKC-Y25-NPN. Here is a sketch of how it was wired up (nomenclature in German, but easily translated).