E9 and flashing reset button/fault LED — Safety temperature circuit tripped

What does E9 mean?

The E9 code appears on the display, and both the reset button and the fault indicator LED flash. This indicates that the boiler's safety temperature circuit has activated, often due to overheating or low water pressure.

• Insufficient water in the heating system (open vented or sealed).
• Seized heating pump.
• Disconnected leads from safety temperature limiters.
• Defective safety temperature limiters or related wiring.

Click steps to track your progress.

1. 1

   Check your heating system type. If open vented, ensure enough water is in the feed and expansion tank. If sealed, verify heating pressure is between 1 and 2 bar.

2. 2

   If pressure is low or water levels are insufficient, top up the system and vent the appliance as per your user manual.

3. 3

   Press and hold the reset button for 3 seconds, then release it. The appliance will restart and attempt to clear the fault.

4. 4

   Check if the heating pump is seized. If you can safely access it, attempt to free it. If it won't start, or if you can't access it, proceed to the next step.

5. 5

   If the problem persists after these steps, switch OFF the appliance and contact a qualified heating engineer to diagnose and resolve the issue.