Glow-Worm Boiler F12 Fault Code
The Glow-Worm fault code F12 relates to the display panel on the PCB and here we have Q & A or require an engineer for an emergency boiler repair.
The Glow-Worm Boiler Fault Code F12 Error Common Q & A
Just below, we have a list of common questions relating to the F12 fault code on the Glow-Worm Boiler.
- What does the F12 fault code mean on my Glow-Worm boiler?
- What does the PCB do on my boiler?
- If my boiler is showing the F12 fault code, is it dangerous?
- If I reset my boiler, will this fix the problem?
- What can cause the F12 fault code to be displayed on my Glow-Worm boiler?
- What is a boiler chip card?
- How can my engineer check that the boiler chip card isn’t the problem?
- If wiring and connections to the PCB aren’t in good condition, how will my boiler engineer know?
- Why would connections on my boiler loosen, or get damaged?
- How will my boiler engineer know if water damage has caused the issue with my Glow-Worm boiler?
- What causes the pump’s seals to leak?
- If I need to replace the PCB on my boiler, how much will I have to pay?
What does the F12 fault code mean on my Glow-Worm boiler
The F12 fault code on Glow-Worm boilers, relates to a printed circuit board fault (PCB). The PCB is having trouble communicating with the display panel.
When this happens, a few problems are going to occur. First, the display might be intermittent, or non-existent. More importantly, any controls on or next to the display panel might stop working.
What does the PCB do on my boiler
Your boiler controls a range of electronic parts. For them to work in harmony, your Glow-Worm boiler needs a PCB. It’s the PCB that receives signals from a range of sensors, and then gives commands for different boiler parts to start or stop operating, or to adjust during operation.
For example, when you turn up the thermostat, the PCB receives a signal from thermistors that monitor water temperature. When it sees that the water is below the temperature being demanded by the thermostat, it will command the gas valve to supply more gas to the burner, heating water up quickly, and increasing the temperature of the flow water.
When PCB faults occur, it can call a whole host of problems. Components will be getting the wrong commands, or no commands at all. That’s going to lead to a boiler that works intermittently.
If my boiler is showing the F12 fault code, is it dangerous
As this is a basic PCB fault, it’s unlikely that your boiler is dangerous. The communication issues between the PCB and the display panel might make the boiler work intermittently, but it’s not immediately dangerous.
Dangerous faults tend to involve the gas valve. If you do smell gas, switch off your appliance and call a Gas Safe boiler repair engineer straight away.
The reason your boiler shows a fault code is to help your engineer find the fault quickly. Fault finding in boilers isn’t easy, especially when it relates to electronics. Without the fault code being displayed, the engineer would have to test dozens of parts, simply to narrow it down to the PCB. That takes time and is going to cost additional cash in terms of labour.
If I reset my boiler, will this fix the problem
It’s likely that your boiler has locked out, before showing the F12 fault code on the display panel. And, whilst modern boilers do have a reset function, it’s not wise to use this without the problem being fixed first.
There might be other problems internally that need fixing (such as internal boiler leaks), as well as the current PCB fault. Without these issues being fixed, more damage could be caused to your boiler, and that’s going to mean more expense.
What can cause the F12 fault code to be displayed on my Glow-Worm boiler
Your boiler engineer doesn’t just need to get your PCB operational again, but also needs to find and fix the root cause of the problem. They’ll need to check:
- The boiler chip card is present and correct
- Wiring and connections to and from the PCB are in good condition
- There are no signs of water damage.
What is a boiler chip card
Many modern boilers use the same PCB unit. The problem is, each boiler is different. Just slotting in these generic PCBs into boilers doesn’t work. For the PCB to work correctly in a boiler, a boiler chip card is used.
It’s the boiler chip card that enables the PCB to communicate with the boiler. And without a boiler chip card, the boiler isn’t going to work.
How can my engineer check that the boiler chip card isn’t the problem
A boiler chip card fault is common if a boiler has suddenly stopped working, or a replacement has been fitted. The PCB on modern boilers needs to be configured. If it’s not been configured, the boiler chip card isn’t slotted into place, or the card has come loose, the boiler isn’t going to work.
So, before jumping to conclusions that the PCB is at fault, your Gas Safe engineer will check the card that communicates with your boiler’s PCB.
If wiring and connections to the PCB aren’t in good condition, how will my boiler engineer know
The next step is to check wiring and connections to and from the PCB. One section of damaged wiring, or a connection that’s not fully secure, is enough to make the boiler’s PCB work intermittently, and that’s going to cause the F12 fault code to be displayed, and the boiler to lock out.
Your engineer can do a quick visual inspection to check the overall condition of the electrics in your boiler. After this, they can test any suspects, using a multi-meter. This will tell your repair company if there are any breaks in the circuit, and therefore, which sections of wiring need to be replaced.
Why would connections on my boiler loosen, or get damaged
The question is, what causes wires and connections to become damaged or loose in the first place? Besides old age, the answer is usually boiler vibrations.
Whilst boiler vibrations are natural, some vibrate more than others, and it could be due to fault. Has your boiler been noisier lately, than it is usually? If it has, this could be the root cause of the problem with your PCB.
Parts such as the pump and fan, both get put under immense amounts of pressure. And, both units sit on bearings, that can wear out over time. Rather than helping the process of the fan/pump’s movement, damaged bearings can hinder it. This can lead to the bearings that grind as they move, making lots of noise, and this noise usually translates to vibrations.
So, if you’ve noticed your boiler being noisy, let your engineer know. On some occasions, the fan and pump can be reconditioned using a bearing kit. This will stop the noise, excess vibrations, and ensure the problem doesn’t happen again.
How will my boiler engineer know if water damage has caused the issue with my Glow-Worm boiler
Besides old age, water damage is one of the biggest killers of boilers. Like many internal boiler problems, water damage typically occurs, due to the pump.
The pump is a sealed unit. That is, until the seals degrade due to years of use and excessive pressure. Once these seals are beyond their working capacity, they’ll leak. And, even if the water from the leak doesn’t drip directly onto the PCB, the moisture inside the boiler can eventually work its way onto a range of electronic components.
If your boiler engineer suspects a leak, they’ll head for the pump first.
What causes the pump’s seals to leak
If this isn’t a case of general wear and tear, it’s likely there has been a catalyst that’s blown the pump seals. Typically, we find this is either a pump that’s on the wrong speed setting, or a build-up of heating sludge.
Modern pumps have multiple settings, three on most units. If you have a small property and set the pump to maximum, that’s needless pressure being put on the pump, and is going to contribute to problems with the seals.
Your boiler engineer will need to check the speed setting on your pump and adjust it if necessary.
Likewise, a combination of airlocks and heating sludge isn’t good for your pump either. These blockages mean that the pump’s ability to circulate water is being restricted.
Heating sludge can be removed from the pump manually. But, it’s going to build-up again quickly, if your boiler repair company doesn’t flush out the system with chemicals.
After flushing the heating system, they’ll use central heating inhibitor. This stays in the heating system to break down this heating sludge. And, if they fit a magnetic system filter, this is going to catch the broken-down particles, stopping them from blocking up important parts such as the heating pump.
If I need to replace the PCB on my boiler, how much will I have to pay
Not all PCB faults are caused by other components in your boiler. It might be that your boiler is old, and the PCB simply needs replacing. Your boiler engineer will be able to fault find, using a multi-meter, to determine whether this is the case.
If it is, you’ll need to replace the PCB. You should expect a new PCB to be anywhere in between £400-500, depending on the exact model of boiler that you own.
Given the cost, it makes sense to weigh up all the options. A new boiler could be as little as £1,800, much more efficient, and come with a long warranty.
So, have your engineer check important components such as the gas valve, pump and fan. If multiple components look like they’re worn, and your boiler has no warranty, it makes no sense to invest 100s of pounds on a repair, only to find more repairs need doing soon.
Other Glow Worm boiler issues
For more boiler issues regarding the Glow Worm then please visit the Glow Worm Boiler Problems And Cures page.