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How-to-Fix-Glow-worm-F5-Fault

The F5 fault code on a Glow-worm boiler often signals an overheating issue, and if ignored, it can leave you without heating or hot water—something no homeowner wants. Resolving this issue quickly and safely is key to restoring warmth to your home.

This blog will help you understand the key steps to diagnose and fix the F5 fault. While some simple checks can be done independently, it's crucial to know when to call a qualified Gas Safe engineer for professional help.



What Does the Glow-worm F5 Fault Mean?

An F5 fault indicates overheating in your boiler.

Overheat-Thermostat-de-surchauffe-115-C-DIFF-pour-Saunier-Duval

This issue is typically caused by low water flow in the system or component malfunctions, such as a faulty thermistor or a blocked heat exchanger.

Causes of F5 Fault on Glow-worm Boilers

Here's a simple explanation of what might be going wrong:

a-new-glow-worm-boiler-without-F5-fault-code

This issue is typically caused by low water flow in the system or component malfunctions, such as a faulty thermistor or a blocked heat exchanger.

1. Low System Pressure

Your boiler needs the right water pressure to work efficiently. If the pressure drops too low, it struggles to function and can trigger the F5 fault code.

2. Faulty Thermistor

The thermistor is like the boiler's temperature sensor. If it's not working properly, the system can't measure the water temperature accurately, which can lead to errors.

3. Blocked Pipes or Heat Exchanger

Over time, pipes and the heat exchanger can get clogged with debris, limescale, or sludge. These blockages restrict water flow, causing the boiler to malfunction.

4. Problematic Pump

The boiler's pump is responsible for circulating water through the heating system. If it's faulty or not working efficiently, water can't flow properly, resulting in the F5 fault.’

5. Pressure Relief Valve Malfunction

This valve helps regulate pressure in the boiler. If it's not functioning correctly, the system might lose pressure, causing performance issues.

6. Faulty Printed Circuit Board (PCB)

The PCB can be considered as the brain of your boiler, controlling its operations. A problem here can disrupt the entire system, leading to error codes like F5.

Understanding the cause of the F5 fault is key to getting your boiler back up and running. If your boiler is acting up, call serviceteam for a professional boiler repair service in London.

Regular servicing can also help prevent these faults and keep your boiler running smoothly for years to come.

Troubleshooting the F5 Fault – Steps Homeowners Can Take

Step 1. Check System Water Pressure

Glow-worm boilers require a certain pressure level to function. Low water pressure is a frequent trigger for the F5 fault.

What to do:

  • Locate the pressure gauge on your boiler.
  • Make sure the pressure is within the manufacturer's recommended range (usually around 1-1.5 bar).
  • If it's too low, use the filling loop to top up the system. Instructions for this can be found in your boiler's manual.
Step 2. Inspect the Pump a-glow-worm-boiler-pump

A faulty pump can restrict water flow, leading to overheating and the F5 fault.

What to do:

  • Turn off the boiler and check if the pump is making unusual noises (grinding or banging).
  • If the pump isn't running smoothly, it may need servicing or replacement by a Gas Safe registered engineer.
Step 3. Look for Blockages

Blockages in the pipes or heat exchangers are common culprits of overheating. These can obstruct water flow, causing the boiler to trip.

What to do:

  • Inspect visible parts of your system for signs of dirt or sludge.
  • Chemically cleaning the system may help, but call a professional for effective powerflushing if needed.
Step 4. Reset Your Boiler

Sometimes, the F5 fault is a temporary system glitch. A simple reset can resolve it.

What to do:

  • Check your Glow-worm boiler for a reset button.
  • Switch off the power, wait a minute, and press the reset button to see if the fault clears.
Safety First!

Always ensure the boiler is powered off before inspecting or attempting minor fixes. For anything beyond basic checks, leave the repairs to a Gas Safe certified professional.

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When to Call a Gas Safe Engineer?

If your boiler still displays the F5 fault after trying these steps, it's time to contact a qualified Gas and heating engineer.

Some issues require a professional diagnosis, such as:

  • Replacing a faulty PCB
  • Fixing a damaged heat exchanger
  • Addressing thermistor issues

Professional engineers have the knowledge, tools, and certifications to access internal boiler components and resolve the issue safely.


Average Repair Costs
Minor issues like adjusting pressure or resetting the boiler may cost between £40-£90. However, replacing components like a PCB or heat exchanger can increase expenses to around £500. Repair vs. replacement recommendations will depend on your boiler's age and condition.

How to Avoid Rip-Offs from Engineers?

When hiring a Gas Safe engineer, always confirm their credentials. They should carry a valid Gas Safe ID card with their photo and registration number.

If you're unsure, you can verify their details using the Gas Safe Register website. A reputable professional will provide accurate advice without pushing unnecessary repairs or replacements.

Call Serviceteam Heating Professionals

Contact Serviceteam Professionals for all your boiler needs. We offer round-the-clock service in London and handle emergency breakdowns and installations alike.
    

How Serviceteam Can Help?

At Serviceteam, we specialise in boiler repairs and maintenance, including diagnosing Glow-worm F5 faults. Our engineers are Gas Safe registered and experienced in offering honest, reliable service.

serviceteam-gas-heating-engineer-is-on-a-boiler-repair-visit

A serviceteam heating engineer visits a home for a boiler repair.


Here's why homeowners trust us:

  • Fast Response: We can arrive within hours to get your heating back on.
  • Transparent Pricing: We offer precise, upfront quotes with no hidden charges.
  • Expert Care: Our engineers have experience in dealing with all Glow-worm boiler issues.

Call Serviceteam or book online to schedule a visit.

Extend the Life of Your Boiler with Regular Maintenance!

Preventative care is the best way to avoid boiler faults. Regular servicing can keep your system running efficiently and identify potential problems before they escalate.

Consider scheduling an annual boiler service to stay on top of your boiler's health. A little maintenance now saves you significant repair costs in the future.

Looking for fast, expert service?
Contact Serviceteam to handle your F5 fault with ease.

To learn more about boiler problems, check out our 'boiler error codes' blog section.

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