What to do
- Reset the lockout once
On boilers with a selector switch, turn it to R and hold it there for at least 5 seconds, then let go. If yours has a reset button, press it until the red light goes out. On boilers reset with the temperature control knob, turn it fully anticlockwise, hold it until the red lockout light goes out, then turn it back to your setting.
When to call a Gas Safe engineer
If the code comes back, call a Gas Safe registered engineer. The fan is inside the boiler, so it's an engineer's job.
A repair visit will usually check the fan, its wiring and the flue.
Before you book
- Note the model and serial number. They're on a label on the data badge, usually under the boiler or behind the front cover.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Checked against
Last reviewed September 2026. Manufacturers update their pages, and your manual is the final word.