Glow Worm F13 Fault – Error Code Guide

The F13 Glow Worm fault is connected to the PCB memory or sensing fault.

This guide will help you to understand potential causes and what can be done to address them.

What Does the Glow Worm F13 Fault Mean?

The F13 fault code means that there has been an issue with the main printed circuit board (PCB). Glow-worm words this fault slightly differently depending on the model of your boiler, either mentioning ‘memory and sensing fault’ or ‘connections fault’.

Whichever phrasing is used, this code will always indicate that the main PCB is unable to function appropriately. As the boiler cannot run without the PCB, it has locked out and displayed the F13 fault. The problem will need to be diagnosed and addressed before it can run again.

What Does the Printed Circuit Board (PCB) Do in a Glow Worm Boiler?

The PCB is responsible for monitoring each part of the heating process, to ensure everything is taking place successfully and safely.

In order to do so, it is connected to a range of sensors within the boiler, such as the thermistors which sense the temperature within the surrounding pipes.

It is also connected to the other electrical components within the boiler, allowing it to register that they are working as needed. For example, the spark electrode which helps to ignite the fuel as it enters the unit.

When your boiler is due to start the heating process, the PCB monitors each of the necessary stages from releasing fuel into the unit to sending heated water into the rest of the home.

Each step that takes place must be confirmed by the PCB before it will permit the next to begin, ensuring that the boiler does not try to continue working when specific parts are malfunctioning. 

What Causes the Glow Worm F13 Fault?

When the PCB is unable to make contact with another component, or registers an issue with one, it will stop the boiler and display a fault code.

In order for this to occur, the PCB must be securely connected to the other parts. The F13 fault indicates that this wiring has become disconnected or damaged in some way, and the PCB has registered that the fault is local rather than surrounding a different component.

If the wires surrounding the PCB become loose or damaged, these necessary connections will either become unstable or severed entirely.

Loose wires are not uncommon within older boilers, as the vibrations within the unit can eventually shake them free of their connections.

These vibrations aren’t always a cause for concern, but if a recent surge in vibrations has caused this problem it could indicate that a part such as the pump is faulty. These larger components can vibrate more than usual if blocked or jammed.

Damage to the wires is also possible, sometimes caused by long term exposure to heat within the unit. Any melting of the wires and connections will lead to decreased stability and potentially failure of the circuit. 

If either loose or damaged connections have caused the F13 fault, you may have noticed it working intermittently in the lead up to the code being displayed. Eventually the PCB will have recognised that the connections are compromised and locked out so they can be repaired.

Though the F13 fault refers to connections, less commonly it can indicate that the PCB has failed entirely, either due to age or damage. Such damage can be caused by moisture, either through tiny particles of condensation over time or from more problematic sources such as leaks.

Why Does My New Boiler Have the F13 Fault?

If you have recently had a new boiler or PCB installed, the issues with memory and sensing could stem from incorrect installation.

PCBs are not automatically configured to a given unit, so must be set up using a product key. If this was not entered, or entered incorrectly, it will be unable to match up with the system to function appropriately.

Another potential configuration issue relates to boiler chip cards. Lots of PCBs are generic rather than branded, which means they can be fitted to many different boilers.

The boiler chip card is a part needed to configure generic PCBs to boilers, so the correct model needs to be fitted for the system to run.

In the case of the F13 fault, the installer may have used the wrong card for your system, or failed to install the appropriate card correctly.

How Can the Glow Worm F13 Fault Be Fixed?

Some loose or damaged connections may be spotted with a visual inspection. However, if not, an engineer can test the wiring around the PCB with a tool called a multimeter.

This takes resistance readings which can be used to tell if power is being transmitted appropriately. 

Reconnecting loose wires is usually a simple job, and any replacement wiring needed will be very cheap. The main costs you can expect will come from labour.

However, an engineer will likely want to ensure that no deeper underlying issue has caused either excess heat or vibration. Should they find that a part such as the pump or heat exchanger is blocked or damaged, further repair works and costs will be needed.

If you have recently had a new boiler or PCB, it would be a good idea to call the installer in the first instance. Loose or damaged wiring is rare in a new unit, so the F13 fault is more likely to have come from PCB or boiler chip card configuration issues.

Your installer should be able to see where they have made an error and correct it without expensive replacement parts, though you may still need to pay a call-out fee depending on their policies.

If all other causes have been ruled out and the engineer believes that the PCB itself has failed, it will need to be replaced.

This may become apparent through testing with a multimeter, though unfortunately there is sometimes some trial and error involved with faulty PCBs, especially when they are working intermittently.

Any damage to the PCB will require further investigation, as moisture could indicate an internal leak coming from another part. There are a few possible culprits, but one common source of leaks is the heat exchanger, which can become cracked by a build-up of limescale.

A new heat exchanger can cost around £300, and prices for flushing limescale out of the system are similar, depending on how many radiators you have in the house.

In these instances, an engineer may suggest that a new boiler is more cost effective than replacing many expensive internal parts. 

How Much Does a New Glow Worm PCB Cost?

The cost of PCBs for Glow Worm boilers varies widely depending on the age and model of the unit.

However, these will always be one of the most expensive components of the boiler whatever its age. You can expect £200 as a minimum price for a new part, but it’s not uncommon for more recently released PCBs to cost up to £500.

If the F13 fault has been caused by an incorrect PCB or boiler chip card installation, you may not need to pay for a replacement as this is the fault of the installer.

However old your boiler is, be sure to check the conditions of the warranty period if you are still within it, as you may be able to save money on repair costs.

The policy may dictate who is able to undertake work on the unit in order to avoid unnecessary costs when the problem cannot be put down to customer misuse.

Is My Glow Worm Boiler with the F13 Fault Dangerous?

The F13 fault is unlikely to mean that your boiler is dangerous if it is only the PCB which has become disconnected or faulty.

The fault code system is intended to stop the boiler from running before it becomes unsafe, indicating to an engineer what needs to be addressed before it may function appropriately again.

However, some fault codes are more likely to indicate potential danger than others, particularly those that relate to the gas supply.

If issues other than PCB failure are currently affecting your boiler, there may still be risk involved, so exercising caution is always a good idea until an engineer has assessed the situation.

Can I Fix My Own Glow Worm Boiler with the F13 Fault?

There is no DIY fix for the Glow-worm F13 fault. As it will require work behind the boiler’s cover, it must legally be undertaken by a registered Gas Safe engineer.

This is a measure which protects untrained individuals from the dangers associated with electricity and gas. If these are interfered inappropriately they can cause further damage to internal parts, as well as potentially risk external danger to human life.

With some other fault codes, you may be safe to attempt resetting the boiler unit. However, performing a reset may force the unit to work intermittently, without fixing the underlying issue which is likely to cause continued problems.

For example, melted connections that have caused the F13 fault may be able to work sporadically, but forcing the boiler to run power through them could lead to burnt out circuits and damage to the PCB.

For the sake of caution, you should only attempt a reset if instructed by an engineer or Glow-worm advisor.

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