Error C6 215

Safety precautions:

- If you smell gas or your carbon monoxide alarm is sounding, leave the property immediately and call the gas emergency number and 999. Do not use the boiler.

- Do not repeatedly reset the boiler more than 2–3 times; repeated resets can mask an underlying safety issue and may damage components.

- Do not remove the boiler case or touch internal electrical components unless you are a Gas Safe registered engineer. Working on gas appliances or live electrics is dangerous and illegal if unqualified.

Initial homeowner checks (safe, no internal access):

1. Note the exact error code (C6 215) and when it appears (on start-up, during run, after reset). This helps the engineer.

2. Perform a standard reset: turn the mode selector to the reset position (flame with a cross) or switch OFF, wait 20–30 seconds, then turn back to normal. If the fault clears and stays cleared, monitor the boiler but arrange a service if it returns.

3. Check the external flue terminal for obvious blockages (bird nest, debris) and ensure airways and vents around the boiler are clear. Do not insert objects into the flue.

4. Check condensate pipe externally (especially in cold weather) for freezing or blockage and thaw gently if frozen. A blocked condensate line can cause unusual behaviour in condensing boilers.

5. Ensure the boiler has mains power and the system pressure is in the normal range (usually 1.0–1.5 bar) — low pressure can cause other faults that complicate diagnostics.

6. If you detect water ingress around the boiler or severe condensation inside the casing, turn the boiler off at the mains and call an engineer.

If the fault persists after the safe checks and a reset:

1. Contact a Gas Safe registered engineer and give them the exact fault code (C6 215), any recent service history, and what you have already tried. This fault usually requires professional diagnostics.

2. What the engineer will typically do: verify the fault by running the boiler through its start-up sequence and reading fan speed and control diagnostics, inspect the fan harness and connector for corrosion or loose pins, test the voltage/control signals to the fan (with the appliance isolated as required), inspect the fan impeller and bearings for wear or water damage, check the flue flow/air pressure switch and associated tubing/sensors, and assess the PCB for faults or error logs.

3. Common professional fixes: clean or replace the fan assembly if bearings or impeller are faulty; replace the fan cable or connector if wiring is damaged; replace the PCB or control module if it is mis-driving the fan or misreading the sensor. The engineer may also rectify external issues like a blocked flue or frozen condensate that are contributing to the fault.

When to stop using the boiler and call immediately:

- If the fault is persistent and the boiler locks out repeatedly after resets.

- If you smell gas or your CO alarm activates.

- If you see water leaking into the boiler or excessive condensation inside the unit.

Final note:

C6 215 is a safety-related fan fault. Initial resets and external checks are reasonable for a homeowner, but diagnosis beyond that (measuring fan speed/signals, replacing fan or PCB, accessing internals) must be carried out by a Gas Safe engineer. Arrange a professional inspection rather than attempting internal repairs yourself.