Error 4 Red Flashes

Safety precautions:

1. If you smell gas, immediately turn off the gas supply at the meter, do not operate electrical switches, ventilate the area, leave the property and call your gas emergency number or the gas emergency service. If in the UK call 0800 111 999.

2. If a carbon monoxide alarm is sounding or you suspect CO, get everyone out of the building and call the emergency services and a Gas Safe engineer. Do not use the boiler.

3. Before any checks, make sure the boiler is safe to approach and there are functioning carbon monoxide alarms in the property.

4. Do not open the boiler casing, do not touch internal components, and do not attempt to replace the fan or any internal electrical parts unless you are a qualified Gas Safe engineer.

Initial checks a homeowner can do:

1. Note the exact error (4 red flashes) and any other display or status lights. Write these down for the engineer.

2. Try a simple reset: locate the boiler reset button or selector, press and hold for 5 to 10 seconds and see if the boiler attempts to restart. If it clears and stays running, monitor it closely for recurrence.

3. Check the external flue terminal and air intake for obvious blockages such as bird nests, leaves, debris, or snow. Clear only external obstructions that are safe to remove from ground level.

4. Check that the boiler has power (isolator switch and consumer unit fuse) and that no external switches have tripped. Do not attempt internal electrical checks.

5. Listen for the fan when the boiler attempts to start. A working fan should spin and produce an airflow sound; a failed fan may make grinding, rattling or no sound at all.

Specific diagnostic and fix steps (homeowner actions and what the engineer will do):

1. Homeowner: After the reset and flue check, if the fault persists switch the boiler off and leave it off. Repeated resets are not recommended.

2. Homeowner: If comfortable and safe, check that external vents/air bricks around the property are not blocked and that the flue terminal is clear. Do not climb on roofs or use tools in unsafe ways.

3. If the fault continues, contact a Gas Safe registered engineer and provide them with the fault code, model, and what checks you have already performed.

4. What the engineer will check and may do: verify fan motor electrical supply and earthing, measure fan current and speed, inspect fan bearings and impeller for wear or obstruction, check wiring and connector integrity, test the fan speed sensor or tachometer, check flue temperature and flue thermistor, examine the PCB for logged faults and run parameter checks, and perform combustion and CO checks after any repair.

5. Repairs that the engineer may perform include replacing the fan assembly, repairing/replacing connector or wiring faults, replacing a faulty flue thermistor or related sensor, or addressing PCB faults if proven. They will also test the system and confirm safe operation before leaving.

When to call a professional and final notes:

1. If the reset does not clear the fault, or if the fault returns, call a Gas Safe registered engineer. Fan faults are safety-critical and require professional diagnosis and repair.

2. Do not use the boiler if it is locked out with this fault or if you suspect any unsafe combustion. Do not attempt internal repairs yourself.

3. Provide the engineer with the fault code (4 red flashes), any observed noises, and the results of your basic checks to speed up diagnosis.

4. If the fault was temporary and cleared, monitor the boiler closely and call a professional if it recurs. Repeated faults indicate an underlying issue that must be fixed.