Rinse water does not reach set temperature; E4 displayed and machine may stop or extend cycle.

Safety first: Disconnect electrical power and allow the booster tank to cool. Booster heaters operate at high wattage and can be hazardous.

• Check incoming hot water: Verify that the building’s hot water supply to the Meiko dishwasher meets the minimum temperature specified by Meiko. Insufficient supply temperature can trigger E4.
• Test booster heater element: Access the booster tank (often at the rear or side). Disconnect the heater terminals and measure resistance. An open circuit indicates a failed element that must be replaced.
• Reset booster safety thermostat: Locate the manual-reset thermostat on the booster tank. Press the reset button. If it trips again, investigate scaling, low water flow, or sensor issues.
• Check booster NTC / temperature probe: Remove the probe from the booster tank and measure resistance. Compare with Meiko’s temperature/resistance chart. Replace if readings are incorrect or if the probe is corroded.
• Inspect heater contactor/relay: In the control box, check the booster heater contactor or SSR for signs of overheating or mechanical failure. Replace if the coil is open or contacts are stuck.
• Reassemble and test: Restore power and run a cycle while monitoring rinse temperature. Persistent E4 after component replacement suggests a control board fault.