Glow-worm F6 Fault Guide for Homeowners: Meaning, Symptoms, Safety, Actions, Causes and Prevention
The Glow-worm F6 boiler fault means there’s a problem with the central heating flow thermistor. You may notice your boiler locking out or inconsistent heating. This fault can lead to overheating, which may damage your boiler’s internal components. Main causes include a blocked pump, low water pressure, and a build-up of limescale in the heat exchanger. Regular maintenance reduces the risk of the F6 fault occurring. Only a Gas Safe registered engineer should carry out work on your boiler, for safety reasons.
Meaning of the Glow-worm F6 Fault
The Glow-worm F6 fault means there’s an issue with the central heating flow thermistor. The thermistor measures the temperature of the water coming out of the boiler and into your pipes and radiators. If the thermistor’s readings are outside normal values, the boiler’s printed circuit board (PCB) will trigger the F6 fault code.
Can this fault pose a safety risk to my home?
The F6 fault itself does not pose a direct safety risk (like a gas leak). But, it shows that your boiler is not working well. This leads to increased wear on the boiler and burning more gas than you need to keep your house warm. It can increase wear and tear on your boiler, too.
What function does the thermistor have in my boiler?
The thermistor monitors the water’s temperature in your heating system. It checks that it’s at the right temperature for your home’s radiators or underfloor heating. Accurate temperature readings are important for optimal boiler performance and energy efficiency.
Can I resolve the F6 fault on my own?
No, you can’t resolve the F6 fault on your own. The fix needs both technical and safety knowledge. Instead, you should contact a Gas Safe engineer. They can diagnose and fix the fault safely and effectively. An engineer will also check for limescale build-up. Similar to having limescale in your kettle, it can impact your boiler’s performance. They will clean or replace affected parts as needed.
Symptoms of the Glow-worm F6 Fault
Several symptoms can alert you to the F6 fault. The obvious one is the F6 error code displayed on boilers with a digital display. You may also notice intermittent heating, where it cuts out unexpectedly. It may fail to reach the set temperature and lead to fluctuations in temperature and comfort, too. There may also be boiler lockouts. These happen when the boiler’s safety measures activate as a result of incorrect temperature readings.
What should I do if my boiler starts to lock out frequently?
Frequent lockouts are a sign of protective measures activated by the boiler system. Contact a Gas Safe registered engineer to safely diagnose and fix your boiler.
Are there any noises I should listen for that indicate an F6 fault?
No specific noises are directly associated with the F6 fault since it relates to temperature sensor issues. If you hear unusual noises from a boiler, such as banging, whistling, or gurgling, there may be some kind of fault or blockage. Again, calling out a boiler engineer is the way to go in these circumstances.
How To Recognise The F6 Fault on Different Types of Glow-worm Boiler
Glow-worm Combi Boilers
On Glow-worm combi boilers, the digital display panel shows the F6 fault. These boilers rely on accurate temperature readings for both heating and hot water modes. This can make a thermistor issue quite disruptive for you.
Glow-worm System Boilers
For system boilers, as with combi boilers, the fault is usually shown on the digital display.
Older Non-Digital Glow-worm Boilers
Diagnosing the F6 fault is hard in old non-digital boilers. This is because they have no display for fault codes. Symptoms may include the pilot light going out or failure to fire up. Full diagnosis requires observation of performance rather than digital codes.
How does the F6 fault affect my boiler’s efficiency?
The F6 fault can make your boiler overheat or underheat water. This raises fuel use and energy bills.
Will the F6 fault affect the lifespan of my boiler?
Yes, unresolved issues, like the F6 fault, can stress the boiler’s parts. This happens in particular if your boiler is overheating water. This can reduce the boiler’s lifespan.
What immediate actions should I take upon noticing symptoms of the F6 fault?
Upon noticing symptoms of an F6 fault, the immediate action should be to contact a Gas Safe registered engineer. Attempting to reset the boiler will not solve the problem, as the causes are all technical in nature.
What to Do When Your Boiler Shows the F6 Fault
When your Glow-worm boiler displays the F6 fault, refer to the User Manual. Always start by consulting the boiler’s user manual for specific guidance on any fault, including the F6. The manual may offer initial troubleshooting steps or describe conditions under which the fault may occur.
Do Not Attempt to Reset Immediately. Don’t reset the boiler without knowing the root cause of the fault. Resetting without fixing the root issue may cause more problems. It may also hide a possibly dangerous condition.
Contact a Gas Safe Registered Engineer. For faults involving internal components or needing technical skill, you need a pro. A Gas Safe registered engineer has the training and credentials to safely diagnose and repair the F6 fault.
Safety Disclaimer
Only take actions recommended in the boiler’s user manual and that you are competent to perform. For technical issues with gas appliances, always use a Gas Safe registered engineer. Tampering with your boiler can pose serious risks to your safety and the operation of the boiler.
Should I try to reset my boiler if it shows an F6 fault?
No, do not attempt to reset your boiler immediately after noticing an F6 fault. Resetting the boiler without addressing the underlying issue may prevent a proper diagnosis. It may also make the problem worse.
Is it safe to turn off the boiler if it displays an F6 fault?
Yes, it is generally safe to turn off your boiler if it displays an F6 fault, especially if the user manual suggests doing so as part of troubleshooting. This can help prevent further damage and is a common safety precaution.
Should I shut off the gas supply when I see an F6 fault?
Shutting off the gas supply is not usually necessary for an F6 fault unless you smell gas or suspect a leak. If you smell gas or fear a leak, shut off the gas. Leave the area and call emergency services or a Gas Safe engineer right away.
Can I fix an F6 fault myself, without professional help?
No, you cannot fix an F6 fault on your own. Seek professional help from a qualified engineer.
The 5 Major Causes of The F6 Fault
There are 5 major causes of the F6 fault: faulty thermistor, limescale build-up, blocked or faulty pump, low water pressure, and wiring issues.
Faulty Thermistor
The thermistor measures the temperature of the water exiting the boiler. If it fails or malfunctions, it can send bad signals to the boiler’s control panel. The panel may think these signals mean overheating and display the F6 fault.
Limescale Build-up
Limescale can accumulate in the heat exchanger, especially in areas with hard water. This build-up can restrict water flow, creating hot spots. These hot spots cause the water to overheat as it passes through. This overheating misleads the thermistor’s temperature readings.
Blocked or Faulty Pump
The pump’s role is to circulate hot water from the boiler through the heating system. A blockage or pump failure can slow this flow. This can cause the boiler to overheat and the thermistor to register the wrong temperature.
Low Water Pressure
Low water pressure in the boiler system can lead to insufficient water flow. Poor water flow causes the boiler to overheat and triggers the F6 fault.
Wiring Issues
Loose or damaged wires between the thermistor and the control board can occur. This can result in unstable or incorrect readings that lead to the F6 fault.
What can I do to prevent limescale build-up?
Regular maintenance helps. Your engineer may suggest water softeners and use descaling agents to reduce limescale build-up. Installing a magnetic filter in the heating system can also capture particles before they deposit on the heat exchanger.
How do I know if the boiler’s pump is blocked or faulty?
Unusual noises, like humming or buzzing, are not normal. They may be signs of pump problems. Also, the heating system may not warm up, or warm up unevenly. A heating engineer can open the pump to check for debris or mechanical wear.
What should I do if I suspect low water pressure in my boiler?
Check the pressure gauge on your boiler; it should typically read between 1 and 1.5 bars when the heating system is cold. If the pressure is below 1 bar, consider repressurising the system or checking for leaks.
How can I identify wiring issues in my Glow-worm boiler?
Inspect the wiring connections to the thermistor for signs of wear, corrosion, or looseness. Ensure that all connections are tight and the insulation is intact. If unsure, a professional should handle this task to avoid further damage or safety risks.
How to Prevent the Glow-worm F6 Fault
Preventing future occurrences of the F6 fault in your Glow-worm boiler comes down to regular maintenance. This will help the system to operate within its designed temperature ranges and identify any faults early.
Regular Maintenance
Annual servicing by a Gas Safe registered engineer will identify and rectify potential issues before they lead to faults.
How often should my boiler be serviced?
Annually. Regular check-ups can prevent minor issues from becoming major problems.
How can I prevent limescale buildup?
Having a chemical flush and installing a water softener or limescale filter can reduce buildup. Talk to your engineer about this.
What should I do if the water pressure is too low?
You can repressurize your boiler using the filling loop. Consult your boiler manual for help with this. If low pressure persists, you may have a leak and this will need professional attention.
Can I check boiler electrical components myself?
For safety, it is best to let a Gas Safe engineer handle electrical checks. This avoids risks and will give you greater peace of mind.
Safety Disclaimer
To keep work on your Glow-worm boiler or any gas appliance safe, efficient, and legal, always use a Gas Safe registered engineer. They have rigorous training and certification to work safely with gas appliances.
- Before work begins, check the engineer’s Gas Safe registration to confirm their qualifications.
- Safety: Choosing a qualified professional helps protect your home. They are trained to protect you from the risks of gas appliances.
Attempting to fix boiler faults or do maintenance tasks beyond basic checks in the user manual can be dangerous. For your safety, always use a Gas Safe registered engineer for any work that goes beyond this.
- Gas Leaks: Incorrect handling of gas appliances can lead to leaks, posing serious risks of fire or explosion.
- Incomplete combustion caused by faulty repairs or adjustments. This leads to the release of carbon monoxide, a dangerous, odourless gas that can be lethal.
Legal and Insurance Issues: Unauthorised repairs can void warranties. They also break safety rules and might void insurance coverage for a claim.