Error 85

Safety precautions:

1. If you smell gas or suspect a gas leak, do not attempt any checks: evacuate the property and call the gas emergency number immediately. 2. Always isolate electrical power to the boiler before opening the casing or touching internal parts. 3. If you are not comfortable with electrical testing or removing covers, stop and call a Gas Safe registered engineer. 4. Do not repeatedly reset the boiler more than once or twice; repeated resets can mask a developing fault and cause further damage.

Initial homeowner checks you can do (no tools or simple tools):

1. Note the exact code displayed (E85 or simply E8 or grouped E83–E87) and when it appeared (start-up, mid-cycle). 2. Try a single reset: press and hold the reset button (usually 5–10 seconds) and observe whether the boiler attempts to restart. If the code returns immediately or after a restart, do not continue resetting. 3. Check that the boiler has mains power and any external isolators are on. 4. Inspect the external flue termination for obvious blockages (bird nest, leaves, heavy snow/ice). Clear any visible obstruction without forcing items into the flue. 5. Ensure the condensate pipe (if external) is not frozen or blocked in very cold weather; if frozen, thaw with warm (not boiling) water. 6. Listen for the fan attempt during ignition sequence—if you can hear the fan spin briefly or not at all, note this for the engineer.

If the basic checks do not clear the fault, further diagnostic steps (recommended for a qualified engineer):

1. Verify the fault history and full sequence of displayed codes and timestamps on the PCB (some models log multiple related errors). 2. With electrical isolation removed only by a competent person: check voltage at the fan connector during a start call to confirm the fan is being driven by the PCB. Measure fan supply voltage and earth continuity. 3. Check fan motor for free rotation: with power isolated, try to rotate the fan impeller by hand to confirm it is not seized or obstructed. 4. Inspect wiring and connectors between fan, air-pressure switch and PCB for loose connections, corrosion or damage. 5. Test the air-pressure switch and tubing for blockages or leaks that would fail to register airflow. 6. Measure fan motor current/impedance to identify a failing motor. 7. Inspect the flue for internal blockages or damage that could impede airflow. 8. If electrical drive to the fan is present but the fan doesn’t run, replace the fan assembly. If no drive is present, further test the PCB: check outputs and any related fuses or relays on the control board. 9. After any fan repair or replacement, verify correct operation over several cycles and confirm no residual faults in the fault log.

When to call a professional and final notes:

1. If the code returns after a single reset or you are unable to carry out the safe checks above, contact a Gas Safe registered heating engineer. 2. Any internal electrical work, fan replacement, PCB fault-finding, or gas-related checks must be done by a qualified engineer. 3. Do not keep resetting the boiler repeatedly; persistent lockouts indicate a fault that needs professional repair. 4. Record the code and any observations (noise, smell, whether the fan tried to run, recent power outages or freezing weather) to give the engineer a clear starting point.

In summary: try the simple safe checks and one reset; if the fault persists, treat this as a condition requiring a Gas Safe engineer to diagnose and repair the fan, wiring, air-pressure components or PCB to restore safe operation.