Why is the Tank Full Light active on the Solar Pump Controller?

1. External Switch Check

The controller has a small external switch on the underneath front right hand corner.
If this switch is in the “O” position, it activates the Tank Full circuit and will stop the pump. This is indicated by the Tank Full light being on and red.
Switch it to the “I” (ON) position to resume normal operation.

The external switch may be faulty and prevent normal operation on the controller. If changing the switch position does not turn the red Tank Full light off, unplug the external switch from the bottom right corner of the circuit board.
Make sure there is no loop wire connecting the TC and TH terminals.

2. Test Without the Sensor Connected

Check that the water level sensor or pressure switch is set correctly and wired into the TC and TH terminals (there is no polarity to this wiring, either wire can go to either terminal).
To set the water level sensor or pressure switch, check the DC pump user manual.
Check that the water level sensor or pressure switch is not sending a false stop signal by disconnecting one or both wires from the TC or TH terminals.
Observe the Tank Full light:
- If it turns off, the sensor or switch is the cause of the false reading.
- If the light remains on, the external switch may be faulty.
- unplug the external switch from the bottom right corner of the circuit board to test.

3. Check for Active Tank Sensor or Pressure Switch

Confirm that the low water sensor is not wired into the TC and TH terminals. This can cause the controller to think the tank is full when it is not.
If a tank full sensor or pressure switch is installed, it might be falsely triggering the Tank Full circuit.
Inspect the pressure switch:
- If a differential pressure switch is in use, make sure the correct terminals are being used.
- Is the opening at the base of the switch’s fitting blocked?
- Has it shifted or been damaged?
- Is the pressure switch showing signs of corrosion.
- Is the cut-off setting too low and causing an early stop signal?
Inspect the water level sensor:
- If your water level sensor has more than 2 wires, check that the correct wires are being used.
- Check that the water level sensor is installed correctly.

4. Inspect Sensor Wiring is correct and not damaged

5. Look for a Stuck Internal Circuit

Like other electronics, the signal relay may get stuck after prolonged power loss or spikes.

Perform a Hard Reset
- With the pump stopped and not running, turn the solar isolator OFF
- Wait 30 seconds
- Turn it back ON
  This will reset the controller and can clear temporary startup issues.

Conclusion:
The Tank Full light being ON is typically caused by:

If none of these solve the issue, contact Commodore Australia’s Technical Support team for further assistance.

If the "Tank Full" light is ON but your tank isn’t full, the pump controller thinks it has been told to stop the pump from running. Here's how to check and fix it: