the water pump is running constantly even when it's not making ice, just a low humming sound

Diagnosis

The constant humming sound coming from your Costway EP24744US is caused by the water pump failing to receive a "stop" signal from the internal water level sensor. In this specific model, the pump is designed to trigger only when the ice-making tray is empty and needs refilling. When the pump runs continuously, it indicates a logic loop where the machine believes the reservoir is empty or the tray is not yet full, despite water being present. This is typically caused by one of two things: a stuck magnetic float switch or mineral scale buildup (calcium/lime) clinging to the sensor probes. If the float switch is jammed by a piece of debris or crystallized minerals, it cannot rise to the "cutoff" position. Consequently, the control board keeps the pump engaged, attempting to fill a tank that is already saturated, which can eventually lead to the pump overheating or water overflowing into the internal electronics. You can confirm this by listening for the pump's rhythmic cycling; if the hum is a steady, unchanging drone regardless of whether the "Ice Full" light is on, the sensor is bypassed or malfunctioning.

How to Fix It

To resolve the constant pumping and reset the sensor logic, follow these precise steps:

1. Immediately disconnect the power cord from the wall outlet. Do not simply turn off the power switch, as the control board needs a full hard reset to clear the pump error.
2. Remove the water reservoir and empty any remaining water into a sink.
3. Carefully tilt the entire machine at a 45-degree angle over a sink to drain any trapped water from the internal pump housing and the delivery tubes.
4. Locate the small float switch (the plastic peg that moves up and down in the water channel). Using a cotton swab dipped in warm water and white vinegar, gently clean around the edges of the float to remove any white mineral deposits that may be pinning it down.
5. Gently flick the float switch upward with your finger to ensure it moves freely and snaps back down. If it feels "gritty," repeat the vinegar cleaning process.
6. Wipe the exterior of the unit and let it sit unplugged for 30 minutes to allow any moisture near the sensor contacts to evaporate.
7. Refill the reservoir with fresh, filtered water and plug the unit back in. The pump should run for a short burst to prime the system and then shut off completely.

If That Didn't Work

• Perform a Deep Descale: If the humming persists, there is likely a heavy calcium buildup inside the internal tubing that the cotton swab couldn't reach. Mix a solution of 50% distilled white vinegar and 50% warm water. Fill the reservoir, run the machine for 10 minutes, then turn it off and let the solution soak inside the internal pump for 2 hours before flushing with fresh water.
• Check for Air Locks: Sometimes a bubble of air gets trapped in the pump head, causing it to run "dry" and hum without moving water, which prevents the sensor from ever being triggered. To fix this, fill the reservoir to the maximum line, then quickly tilt the machine forward and backward several times while the pump is active to force the air bubble out.
• Inspect the Control Board: If the pump runs even when the reservoir is completely removed, the issue is a short circuit on the main PCB (Printed Circuit Board). Check for any signs of water ingress or corrosion on the board. If you see green oxidation, clean it with 90% Isopropyl alcohol and a soft toothbrush.
• Replace the Water Pump: If the humming sound is accompanied by a burning smell or the pump is vibrating violently without moving water, the internal impeller may have snapped. In this case, the pump assembly needs to be replaced with a compatible 12V DC water pump.

Heads Up

• Avoid Hard Water: Always use filtered or distilled water. The EP24744US is highly susceptible to mineral buildup, which is the primary cause of sensor failure and pump burnout.
• Weekly Maintenance: Run a vinegar flush once every two weeks to prevent the float switch from seizing.
• Avoid Overfilling: Never fill the reservoir past the "Max" line, as this can cause water to seep into the sensor housing and trigger erratic pump behavior.
• Power Cycle: If the machine behaves strangely after a power surge, always unplug it for 60 seconds to reset the internal logic board.