What to check, in order
- Check the pressure gauge
Baxi says it should read between 1 and 2 bar. If it's below 1 bar, top it up with the filling loop.
- Reset the lockout
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 it overheats again, call a Gas Safe registered engineer. A jammed pump is a job for them.
A repair visit will usually check the pump, the flow of water round the system and the overheat thermostat.
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
- Baxi: boiler error codes (list for engineers)
- Baxi: what should my boiler pressure be set at
- Baxi: how to reset a Baxi boiler
Last reviewed September 2026. Manufacturers update their pages, and your manual is the final word.