Glow-worm F12 Fault Code Guide: Meaning, Symptoms, Actions, Repair Costs, Causes and Prevention

The Glow-worm F12 fault code indicates a communication error between the main PCB and the display PCB. You may notice intermittent or non-existent display and non-functioning controls. There are no immediate safety risks, but addressing the fault promptly is crucial. Main causes include wiring issues, water damage, and general wear and tear. Regular maintenance and inspections can prevent this fault. Always use a Gas Safe registered engineer for repairs. In the next section, we will explain the meaning of the fault in more detail.

Meaning of the Glow-worm F12 Fault

The Glow-worm F12 fault code means that there is a communication error between the main printed circuit board (PCB) and the display PCB. It disrupts the signals sent from the main PCB to the user interfaces. This disruption prevents the boiler from operating. This can be caused by issues such as loose wiring, damaged connectors, or faults in the PCBs themselves. External factors like water damage or excessive vibration can also contribute.

What is a PCB in a Glow-worm boiler?

The PCB, or printed circuit board, is the central control unit of the boiler. It manages signals from various sensors and components, ensuring the boiler operates efficiently. The main PCB sends commands to start or stop operations based on the data it receives.

What happens when the Glow-worm boiler F12 fault occurs?

When the F12 fault occurs, the communication between the main PCB and the display PCB is disrupted. This can cause the display to show error codes, become intermittent, or stop working altogether. As a result, the controls on the display panel may also become non-functional.

Is the Glow-worm boiler F12 fault dangerous?

The F12 fault itself does not pose an immediate safety hazard. However, any boiler malfunction should be addressed promptly to prevent further issues.

Symptoms of the Glow-worm F12 Fault

There are 5 main symptoms of the Glow-worm F12 fault:

1. Intermittent Display: The boiler’s display panel may show intermittent or flickering information.
2. Non-Functional Controls: Controls attached to the display circuit board may stop responding.
3. Boiler Lockout: The boiler might enter a lockout state, where it shuts down and refuses to restart.
4. Error Code Display: The panel will show the F12 fault code.
5. No Heating or Hot Water: The boiler is unlikely to provide heating or hot water. This isn’t great if you need to do the washing up!

How to Recognise the F12 Fault on Different Types of Glow-worm Boiler

Glow-worm Combi Boilers

On Glow-worm Combi boilers, the F12 fault is displayed on the LED screen. It’s also possible that the display might flicker or blink on and off intermittently. You may also notice that the controls become unresponsive. The boiler fails to produce heat or hot water.

Glow-worm System Boilers

For Glow-worm System boilers, the symptoms are similar to those on Combi boilers. The digital display will show the F12 fault code, and the controls may become unresponsive. There may be a noticeable lack of heating or hot water, and the boiler may shut down or lock out, preventing it from restarting.

Older Non-Digital Glow-worm Boilers

On older non-digital Glow-worm boilers, recognising the F12 fault can be more challenging. These boilers may not display specific fault codes. Instead, you might notice the boiler is not heating water for your radiators or taps. The control panel may be completely unresponsiveness. You’ll need professional inspection to diagnose the F12 fault on these older boilers.

What’s the Typical Cost to Repair the F12 Fault?

The typical cost for repairing the F12 fault is normally around £260, with a range from £100 to £300. The fault generally means replacing a board, which is a major expense and so pushes the repair towards the top of the range. The repair fee also covers a realistic callout fee, along with the time to diagnose and replace parts as necessary

What to Do When Your Glow-Worm Boiler Shows the F12 Fault

When your Glow-worm boiler displays the F12 fault, turn it off to prevent any further damage. Do not attempt to fix the wiring yourself. Electrical repairs require specific expertise and can be hazardous. Always contact a Gas-Safe registered engineer to handle any wiring issues.You’ll need to call a Gas Safe registered engineer to diagnose and repair this fault.

How to Turn Off Your Glow-worm Boiler Safely for the F12 Fault?

To turn off your Glow-worm boiler safely, locate the power switch or button on the boiler unit. Switch it to the off position.

Can You Reset a Glow-worm Boiler for the F12 Fault?

Resetting your boiler can sometimes clear minor faults. Locate the reset button on your boiler – often red. Press and hold it for a few seconds until the boiler attempts to restart. If the F12 fault persists, further professional diagnosis is necessary.

The 5 Major Causes of The F12 Fault

The F12 fault in Glow-worm boilers is mainly caused by wiring issues, water damage, boiler chip card problems, excessive vibration, and general wear and tear.

1. Wiring Issues

Wiring issues are a common cause of the F12 fault. Loose or damaged wires can interrupt communication between the main PCB and the display PCB. Over time, connections can become loose due to vibrations and general use. Inspecting and securing all wiring connections can often resolve this issue.

2. Water Damage

Water damage can severely affect the electronics in your boiler. Leaks from internal components, such as the pump, can cause moisture to reach the PCBs. Even minor leaks can lead to significant issues if not addressed promptly. Regular maintenance and inspections help identify and fix leaks early, preventing water damage.

3. Boiler Chip Card Problems

The boiler chip card is essential for the PCB to function correctly. If the card is not properly inserted or becomes faulty, it can cause the F12 error.

4. Excessive Vibrations

Excessive vibrations within the boiler can cause components to become loose or damaged. This is particularly true for older boilers or those with worn-out parts, such as the pump or fan. Addressing unusual noises or vibrations can help to keep the boiler working well.

5. General Wear and Tear

Over time, all boilers experience wear and tear. Components such as PCBs, wiring, and connectors can degrade, leading to faults like F12. Regular servicing is key.

Preventing Future F12 Faults

Use a professional Gas Safe registered engineer to service your boiler annually. These yearly maintenance checks include inspection, cleaning, and repair as needed. This proactive approach helps identify potential issues early, reducing the risk of faults.

Consider a boiler service contract for continuous support and peace of mind. Service contracts typically include annual inspections, priority call-outs, and repairs. Ongoing care ensures your boiler operates efficiently and safely,.

Disclaimer

Any work beyond the operations described in your user manual should be performed by a Gas Safe registered engineer. Attempting repairs or maintenance yourself can be dangerous and may void warranties. Always seek professional assistance to ensure the safety and proper functioning of your boiler.