my ice maker keeps flashing the 'add water' light but the tank is definitely full

Diagnosis

The "Add Water" indicator on a Della Portable Ice Maker is triggered by a magnetic float switch located within the water reservoir. This system relies on a small, buoyant plastic piece containing a magnet; when the water level is sufficient, the float rises, triggering a reed switch that signals the control board to begin the freeze cycle. When the light flashes despite a full tank, it means the sensor is failing to register the "high" position, causing the machine to believe it is empty to prevent the pump from running dry and burning out.

This failure typically occurs due to one of three reasons: mineral buildup (calcium/scale) creating friction that "pins" the float in the down position, a physical obstruction like a piece of plastic flashing from the manufacturing process, or a displaced magnet. You can confirm this by looking at the float—if it is sitting at the bottom of the tank while the tank is full of water, the sensor is physically stuck. If the float is floating perfectly but the light is still flashing, the reed switch has likely failed or the magnetic connection is interrupted.

How to Fix It

To resolve a stuck float sensor and clear the "Add Water" error, follow these precise steps:

1. Disconnect the unit from the 110V power outlet to prevent any electrical shorts during cleaning.
2. Remove the water reservoir entirely from the main chassis.
3. Locate the white plastic float assembly. Depending on your specific Della model, this is either a vertical cylinder housed in a small chamber on the side of the tank or a floating disc at the bottom.
4. Gently push the float down and release it several times. If you feel resistance or a "gritty" sensation, mineral deposits are locking the mechanism.
5. Fill a basin with a mixture of one part white distilled vinegar and three parts warm water. Submerge the float assembly in this solution for 20 minutes to dissolve calcium carbonate buildup.
6. Use a soft-bristled toothbrush to scrub the walls of the float chamber, ensuring there is no slime or scale preventing the float from sliding freely.
7. Rinse the reservoir thoroughly with fresh water to remove all vinegar residue.
8. Reinsert the reservoir, ensuring it clicks firmly into the base. If the reservoir is not seated perfectly, the sensor may not align with the internal trigger.
9. Plug the unit back in and wait 60 seconds for the control board to reset.

If That Didn't Work

• Check for Air Locks: Sometimes air bubbles get trapped in the pump line, mimicking a "low water" state. Tilt the machine gently forward and backward while it is running to force air bubbles out of the internal plumbing and allow water to reach the sensor.
• Inspect the Magnet: If the float is moving freely but the light persists, the internal magnet may have shifted. Try using a strong neodymium magnet and sliding it along the outside of the reservoir where the float is located. If the "Add Water" light turns off, the internal magnet in the float is dead and the reservoir needs replacement.
• Hard Reset the Control Board: Unplug the machine and leave it disconnected for at least 30 minutes. This clears the volatile memory of the control board, which can sometimes "hang" on an error state even after the physical condition (low water) has been corrected.
• Verify Water Temperature: If you are using extremely cold water (below 40°F), some Della sensors may behave erratically. Try using room-temperature filtered water to see if the sensor registers correctly.

Heads Up

• Never use abrasive scouring pads or bleach to clean the reservoir, as this can scratch the plastic and create microscopic grooves where mold and scale build up faster.
• To prevent future "Add Water" errors, descale the machine every 30 days using a commercial citric acid solution or white vinegar.
• Always use filtered water. Tap water with high mineral content (hard water) is the primary cause of float sensor failure in portable ice makers.
• Ensure the machine is placed on a perfectly level surface; a slight tilt can cause the float to rub against the side of its housing, causing intermittent "Add Water" flashes.