Display shows E0; heater is unresponsive or shuts down unexpectedly.

Safety: Turn off power at the breaker. Do not touch the PCB while power is on.

• Power cycle: Turn off power for at least 30 seconds, then restore. Observe whether the E0 code clears temporarily.
• Inspect control compartment: Remove the front cover and check for signs of water ingress, condensation, or corrosion on the control board and connectors.
• Check all plugs: Gently press on all multi-pin connectors to ensure they are fully seated. Look for burnt or discolored pins.
• Verify supply voltage: Use a multimeter to confirm that the incoming voltage matches the rating on the heater nameplate and is stable.
• Dry and clean: If moisture is present, carefully dry the area and correct the source of leaks (e.g., leaking fittings above the board).
• Board replacement: If the error persists and no external cause is found, the control board likely needs replacement by a qualified technician, as programming and safety checks are required.