Why is the Low Water Light Flashing on a Submersible Pump Controller?

• If a pump is running and the water level drops below the low water level sensor, the red Low Water light will turn on and stay solid.
• The controller will stop the pump and wait for the low water sensor to be resubmerged by water.
• Once the sensor is resubmerged the Low Water light will begin to flash, indicating that it is using the 30-minute restart delay.
• Once the 30-minute delay is finished, the Low Water light will stop flashing, and the controller will restart the pump.
• This feature helps to prevent damage to the motor, damage to the impellers, and other dry-run wear and tear.

Inside the pump controller:

• Ensure the sensor wires are firmly connected to the WC and WH terminals.
• Either wire can go in either terminal (no positive or negative polarity).
  • Check for:
    • Loose wires
    • Rust, corrosion, or water damage
    • Pests such as ants, spider, etc.
    • Animal damage to cables

Clean and secure any questionable connections or replace damaged cables.

If you're using a water level sensor, make sure the factory installed red bridging wire between the WC and WH terminals has been removed.

• This red bridging wire is used for dry testing or non-sensor setups.
• Leaving it connected overrides the sensor and will interfere with proper function the low water sensor or flow switch.

Remove this wire to ensure the controller only responds to the sensor or switch signals.

Incorrect installation or dropping water levels are common causes.

• For submersible pumps, install the Low Water sensor at least 1 metre above the pump intake.
• The sensor must be fixed in place vertically with the wire coming from the top of the sensor. Do not install it with the wire coming from the bottom and then running up towards the surface.
• A sensor that isn’t fully submerged or is touching the tank wall might give false “low water” signals.
• Ensure the sensor is:

• Installed vertically.
• Fully submerged in water.
• Not floating freely.
• Not sitting in air.
• Connected to the WC and WH terminals.

If the water sensor is now properly submerged, you can either:

Option A: Let the controller automatically restart the pump after the 30-minute delay.
Option B: Manually clear the timer and restart the pump:

• Turn OFF the solar isolator.
• Wait 30 seconds.
• Turn the solar isolator ON again.

This will clear the restart delay, and the controller will attempt to restart the pump. If there is another reason for the controller to stop the pump (e.g. the tank full light is on), the controller will not restart the pump.

• If you suspect the sensor might be faulty, place a loop wire between the WC and WH terminals.
  • If the Low Water light starts flashing or turns off:
    • The low water sensor is not in water
    • Water is not being pushed through the flow switch
    • Or the switch/sensor is faulty and needs replacing

Important: Remove the jumper after testing — don’t leave it permanently installed.

Sensor Failure

If the sensor is underwater, the wiring is correct and not damaged, the loop wire test worked but the light stays on when the low water sensor or flow switch is installed, the sensor is faulty and need replacing.

If the water level sensor is underwater, the wiring is correct and not damaged, the loop wire test worked but the light stays on when the low water sensor or flow switch is installed, the sensor is faulty and need replacing.

Conclusion:
A flashing Low Water light means your controller is in a 30-minute restart delay to protect the pump and allow the water source more time to replenish itself.

This is normal and safe.

To fix it:

• Check the sensor position.
• Inspect the wiring.
• Confirm the red bridge wire was removed.
• Reset the system or wait 30 minutes.

If the Low Water light is still flashing, the sensor or controller are likely faulty. Contact Commodore Australia’s Technical Support team for further assistance.

Phone 1300 669 256 or email support@commodoreaustralia.com.au