E15 error; unit may not detect water even when the reservoir is full.

Safety first: Disconnect power before working in the water reservoir area.

Steps to address E15:

• Clean the reservoir: Empty the tank and wipe it clean. Remove scale or slime that may insulate the sensor.
• Locate low water sensor: On many Tristar models, this is a pair of metal probes or a small float near the bottom of the reservoir.
• Clean sensor contacts: Use a soft brush and descaling solution to clean metal probes. Rinse thoroughly.
• Inspect wiring: Check the harness from the sensor to the control board for damage or loose connectors.
• Replace sensor if faulty: If cleaning does not help and the sensor tests open or shorted, install a new Tristar low water level sensor.
• Reassemble and test: Refill the reservoir, restore power, and confirm the unit recognizes water and E15 is cleared.