Error E12

Safety precautions:

- If you smell burning or see smoke, turn off the boiler at the mains isolator and the gas supply if it is safe to do so, ventilate the area and call a Gas Safe registered engineer immediately.

- Do not open the boiler casing or touch internal components or wiring unless you are a qualified engineer. Mains voltage and gas are dangerous.

Initial homeowner checks (safe, non-intrusive):

1. Note the exact error code and any other lights or messages on the display. Photograph the display for the engineer.

2. Try a basic reset: if your boiler has a reset button press and hold it as per the manual; on some Baxi models move the selector to R (Reset) and hold for about 5 seconds; on models with a thermostat knob turn it fully anticlockwise then back to your setting. Wait a few minutes to see if the fault clears.

3. Check the house fuse/consumer unit and the boiler fused spur to ensure the boiler has mains power. Check any external timers, thermostats and batteries in wireless controls — remove a simple cause such as a dead thermostat battery.

4. Look for obvious external signs: visible water leaks around the boiler, excessive rattling or loose panels, and whether the fan seems noisy or the boiler makes unusual sounds when it attempts to start. Do not dismantle to inspect the PCB.

5. If the boiler display is blank (no lights) this can indicate loss of power to the PCB — isolate mains and call an engineer; do not attempt internal repairs.

Specific diagnostic and fix steps (to be performed by a Gas Safe engineer):

- Confirm and log the fault using the boiler’s diagnostics and any service menus. Check fault history.

- Verify mains supply and the boiler’s internal fuses and voltage rails feeding the PCB. Inspect incoming wiring and the fused spur.

- Visually inspect the PCB for burnt components, corrosion, water staining, or detached/ cracked solder joints. Check for residue from leaks and signs of overheating.

- Check related components the PCB monitors: fan and air pressure switch operation, gas valve comms, ignition electrodes, and NTC sensors. Faults in these parts can register as PCB errors.

- Check connectors and wiring looms for secure connections and signs of chafing or vibration damage. Address any loose or corroded connectors.

- If solder joints are cracked the engineer may attempt targeted reflow or re-soldering, but practical repair often requires PCB replacement for reliability.

- If PCB replacement is required the engineer will fit the correct part, configure/program the PCB (product code or serial programming if needed), and run full startup and safety checks. They will also fix any root cause (e.g., stop a leak, secure a vibrating component) to avoid repeat failure.

When to call a professional:

- If the fault does not clear after a safe reset and basic checks, or if you see water, burning smells, repeated lockouts, or a blank display, contact a Gas Safe registered engineer. PCB faults involve live electrical work and gas components and must be handled by a qualified technician.

Additional notes:

- If the boiler is new or recently serviced check warranty/installation paperwork before any paid repair — manufacturing faults may be covered.

- Record model/serial number, exact fault code, and symptoms to give to the engineer. Do not attempt internal repairs yourself. No repair cost estimates are provided here.