Error D.71

Safety precautions:

1. Do not open or attempt internal repairs on the boiler or gas components. If you are not a Gas Safe registered engineer, do not remove panels, probes, or wiring.

2. If you must power the boiler down for safety reasons, use the main on/off switch installed on site. If you isolate the boiler for extended periods in cold weather, be aware of frost risk to the heating system.

3. Ensure you have access to the operating instructions or have someone available to help if unsure.

Initial checks a homeowner can do:

1. Look at the boiler display and confirm D.71 is the only message showing. Note any additional F‑codes if present; those require an engineer.

2. Check the heating flow temperature setting on the boiler controls (the radiator icon or the heating flow temperature menu). If an external controller (room thermostat or wired controller) is fitted, check its settings too.

3. Verify whether the boiler has been placed into a special maximum output or chimney sweep mode (sometimes enabled for servicing/testing) — this can be done through the front control panel/menu on most ecoTEC units.

Specific diagnostic and fix steps you can try:

1. Reduce the heating flow temperature: on the boiler front panel press the heating button (radiator symbol) to view the target flow temperature. Use the plus/minus buttons to reduce the target to a normal value (commonly 55–65 °C for radiators, or lower according to your system) and press the confirm/OK button. If a controller is connected, set the maximum on the boiler to the permitted value and set the actual desired temperature on the controller.

2. Exit maximum output / chimney sweep mode: if the boiler is in maximum output operation, navigate the control menu (open the front flap if fitted) and return the operating mode to 'normal' or the previously used mode. Consult the operating instructions pages on 'Maximum output operation' and 'Setting the heating flow temperature' for exact button sequences.

3. If the display does not accept changes or the temperature control appears physically stuck (knob or buttons unresponsive), try a simple reset: press the fault clearance/reset button as described in the manual (press for one second). The diagnostic D.71 may clear after you change the setting. Do not perform resets repeatedly if an F‑code appears or if the boiler shows other fault symptoms.

4. After changing settings, observe the boiler for a short period: check that radiators warm to expected levels, no unusual noises occur, and no other fault codes appear. If the boiler heats normally and D.71 disappears, no further action is required.

When to call a professional:

1. Call a Gas Safe registered engineer if the control or buttons are unresponsive, the D.71 message remains after you have returned the settings to normal, or if other fault codes (F‑codes) appear at the same time.

2. Call an engineer if you are unsure about navigating the boiler menu, or if the boiler behaves strangely after changing settings (persistent overheating, frequent lockouts, or safety shut‑downs).

3. Do not attempt to adjust or repair gas valves, internal sensors (NTCs), wiring harnesses, or to remove panels yourself — these are job for a qualified technician.

Notes and cautions:

1. D.71 indicates a user/configuration condition rather than an internal hardware failure in most cases; changing the heating flow temperature or exiting maximum output mode normally resolves it.

2. If you see other error codes alongside D.71, treat those according to their severity and contact a professional promptly. If in any doubt about safety or operation, switch the boiler off and call a qualified engineer.