When your gas boiler’s fan stops working, it can lead to a range of issues, from the heating and hot water not coming on to the pilot light failing to ignite. Understanding the potential causes and the technical specifications involved in diagnosing and repairing the problem is crucial for a successful resolution.
Causes of a Gas Boiler Fan Not Working
1. Faults in the Circuit Board
The boiler’s printed circuit board (PCB) plays a vital role in controlling the fan’s operation. Issues with the PCB, such as loose wiring connections or a faulty PCB itself, can prevent the fan from functioning correctly. A Gas Safe engineer should inspect the PCB using a multi-meter to diagnose the problem accurately. Common PCB faults include:
– Damaged or corroded PCB components
– Faulty microcontroller or other integrated circuits
– Loose or damaged wiring connections to the PCB
2. Faults with the Air Pressure Switch
The air pressure switch is responsible for sending signals to the fan, instructing it to operate. If the air pressure switch malfunctions, the boiler may fail to start, and the fan will not receive the correct signal. Replacing the air pressure switch is often the solution in such cases.
3. Blockage in the Condensate Pipe
Frozen condensate pipes can cause fluctuations in air pressure, leading to issues with the fan’s operation. The condensate pipe is responsible for draining the water produced during the combustion process. If this pipe becomes blocked or frozen, it can disrupt the air pressure within the boiler, preventing the fan from working correctly. Thawing the pipe and insulating it to prevent future freezing is the recommended solution.
4. Low Fan Speed
If the fan speed is too slow, it can cause the pilot light to blow out or the boiler to lock out. This can be due to a problem with the fan’s speed control or a fault in the PCB’s programming. Adjusting the fan speed, either manually or through the PCB settings, may resolve the issue.
5. Loose Connections
Vibrations from the boiler can cause wiring connections to become loose over time. This can disrupt the power supply to the fan or the control signals it receives from the PCB. Securing or fastening the connections back in place can often fix this problem.
6. Damage Caused by Leaks
Leaks within the boiler can damage the fan and other components. A Gas Safe engineer should thoroughly inspect the boiler for any signs of leaks, stop them, and address any damage caused to the fan or other parts.
7. Malfunctioning Fan
If the fan is over 5 years old, it may be reaching the end of its lifespan and become faulty. Boiler fans typically have a lifespan of 5-10 years, depending on usage and maintenance. Repair kits are available, but replacement is often the most practical solution, especially if the fan is difficult to access or the repair is complex.
8. Faulty Circuit Board
A faulty PCB can prevent the fan from functioning altogether. In most cases, the PCB needs to be replaced, which can be an expensive repair. Before replacing the PCB, a Gas Safe engineer should thoroughly test the circuit board to confirm the issue.
Symptoms of a Gas Boiler Fan Not Working
- The heating and hot water are not coming on.
- The pilot light is not igniting.
- The boiler sounds like it is coming on but nothing happens.
Technical Specifications and Testing
Testing the Fan
Before attempting any repairs, ensure the power to the boiler is switched off. Disconnect the fan’s leads and check for a permanent 240-volt supply to the fan using a multi-meter. If there is no power, the issue may be with the electrical supply rather than the fan itself.
Pulse Width Modulation (PWM) Signal
The fan in a modern gas boiler receives a Pulse Width Modulation (PWM) signal from the circuit board, which controls the fan’s speed. Testing this PWM signal is crucial to diagnose any fan-related issues. A Gas Safe engineer can use a multi-meter or an oscilloscope to measure the PWM signal and ensure it is within the expected range.
Repair and Replacement Costs
Repair Cost
The repair cost of a boiler fan is often similar to the cost of replacement due to labor fees. If the repair is complex, involving the replacement of multiple components, it might be more cost-effective to replace the fan altogether.
Replacement Cost
Replacing a boiler fan can be an expensive repair, especially if it involves replacing the entire PCB. Costs can range from £500 to £1,000 or more, depending on the brand and type of boiler. The fan itself may cost between £100 and £300, but the labor and additional parts required can significantly increase the overall cost.
Reference Links
- https://247homerescue.co.uk/blog/boiler-fan-faults-reasons-and-solutions/
- https://www.youtube.com/watch?v=3dTlYRwDiEc
- https://www.youtube.com/watch?v=0K68-M841RM