Water heater will not start; display shows E01 and heating does not engage

Safety first: Turn off the circuit breaker and isolate electrical power before opening the unit. Close the cold water isolation valve.

Steps:

• Check water supply and filters: Open the cold inlet isolation valve fully. Remove and clean the inlet filter/strainer on the Dimplex water heater (usually at the cold inlet union). Rinse debris and reinstall.
• Verify minimum flow: Open a hot tap fully and confirm strong flow. If flow is weak, check house supply pressure, stop valves, and any external filters or pressure-reducing valves.
• Inspect flow sensor/switch: Remove the front cover. Locate the flow sensor or paddle flow switch on the cold inlet manifold. Check for scale or debris; clean gently. Ensure the paddle or turbine spins/moves freely.
• Check wiring: Inspect the harness from the flow sensor to the main control PCB for loose connectors, corrosion, or damaged insulation. Reseat connectors firmly.
• Reset and test: Restore power, open a hot tap, and see if E01 clears. If the code persists after cleaning and wiring checks, the flow sensor/switch is likely defective and should be replaced.

When to call a technician: If you are not comfortable opening the unit or measuring continuity on the flow sensor, contact a qualified technician.