D4 286 — Boiler return temperature sensor detected temp higher than 105°c

What does D4 286 mean?

The boiler return temperature sensor has detected a temperature exceeding 105°C. This is a critical safety warning indicating potential overheating in the return circuit.

• Poor water circulation.
• Blocked pipework or heat exchanger.
• Defective return temperature sensor.
• Pump failure.

Click steps to track your progress.

1. 1

   Turn off the boiler immediately and allow it to cool down.

2. 2

   Check the system pressure and ensure it is within the normal operating range.

3. 3

   Ensure all radiator valves are open to facilitate water circulation.

4. 4

   Contact a Gas Safe registered engineer to diagnose the cause of overheating and rectify the issue.