Ahorn A 690 – MHCP_LED Display Model B: Info button responds, but all info fields (tank levels, etc.) remain dim

[Baumeister_0815]

Subject: Ahorn A 690 – MHCP_LED Display Model B: Info button responds, but all info fields (tank levels, etc.) remain dim

Hello,

I have an Ahorn A 690 equipped with an MHCP_LED Display Model B. Year 2023. When I press the information button, it is acknowledged (it activates), but all information fields such as tank levels, battery status, etc., remain dim/darker and do not show proper readings. What could be the cause?

Context and observations

The panel appears to have power because the button press is recognized, but the actual measurement and display data don’t show up.
This suggests the panel may be powered while the measurement signals or communication from the central electrical unit (EBL/charger/control unit) are not reaching it, or a common reference/ground/ supply for the sensors is missing.
The issue affects all info points at once, which points to a common/central cause rather than multiple individual sensor failures.

Likely root causes (from similar cases)

12 V habitation supply too low or switched off: Some panels stop measuring below a voltage threshold or when the 12 V main for the living area is off.
Blown fuse for the panel, sensor supply, or reference voltage within the EBL.
Loose/oxidized communication cable between the panel and the EBL (often an RJ-style connector) or a damaged cable.
Missing common ground or sensor reference supply (5 V/12 V) for the tank probes and other sensors.
Night/dim mode or sleep state causing very low brightness or disabled measurements when the board supply is off.
System “hang” after battery work, deep discharge, or long storage that clears with a power-cycle/reset.

Planned/basic checks

Ensure the 12 V habitation supply is switched on at the panel/EBL.
Measure the habitation battery directly at the terminals. Target: approx. 12.4–12.8 V at rest; below ~11.5–11.8 V can cause malfunctions.
Connect to shore power/charger and see if the behavior changes.
Check all relevant fuses at the EBL (panel/display, sensors/level/tank probes, interior 12 V). Ideally test with a meter or swap like-for-like, not only visual inspection.
Reseat the panel cable on both ends, inspect for corrosion, and check the cable for kinks/cuts.
Inspect main ground points (Klemme 31) for secure, clean connections.
Perform a reset: switch off the 12 V system, then disconnect the habitation battery negative terminal (or pull the EBL main fuse) for 2–5 minutes, reconnect, and retest.
If possible, check whether a sensor supply (5 V or 12 V, depending on system) is present at the tank probes; if absent, trace back to the EBL/fuse.
Verify whether other panel-controlled functions (12 V master, water pump, lights) still operate normally.

Questions to help pinpoint the issue

Which EBL/charger/control unit is installed in this Ahorn A 690 (e.g., brand and model)? Is there a wiring/pinout reference for the MHCP_LED Display Model B connection to the EBL?
Is there a documented minimum battery voltage below which the MHCP_LED panel suppresses measurements?
Are there specific fuse numbers/labels in this model that protect the panel and the sensor reference supply?
Is there a known night/dim mode that could cause all info fields to appear very dim, and how can it be toggled off?
Is there a recommended reset procedure or firmware update for the MHCP_LED Display Model B?
Is there a diagnostic mode or error code readout for this panel/EBL combination?
Have there been known cases of cable/connector issues (RJ-style) on this model and a recommended replacement part?

If you need additional details, I can share the exact EBL brand/model, recent work done (battery change, storage period, any signs of moisture), and whether shore power changes the behavior. Thank you very much for your support.

Best regards,
Paul Baumeiste

[SimoneR]

Hello
To solve the problem you need to restart control panel by 4pin supply connectors. You need to disconnect and reconnect it and the problem solved.