Viessmann Boiler FC Fault Code
The Viessmann fault code FC could be related to the gas valve, fan, flue or PCB and here we have Q & A or require an engineer for an emergency boiler repair.
The Viessmann Boiler Fault Code FC Error Common Q & A
Just below, we have a list of common questions relating to the FC fault code on the Viessmann Boiler.
- What does the FC fault code mean on my Viessmann boiler?
- Can the FC fault code be fixed without a boiler engineer?
- What problems can occur with the gas valve on my boiler?
- How much will a new gas valve cost to fit on my Viessmann boiler?
- Could wiring be the issue with the gas valve on my boiler?
- What other issues could the gas valve have that cause the FC fault code to be displayed?
- What does the fan have to do with the FC fault code being displayed on my Viessmann boiler?
- My boiler’s fan doesn’t have power, what’s the fix?
- What is the flue, and how could this cause the FC fault code to be displayed?
- My boiler repair company thinks the PCB is causing the FC fault code to be displayed, does this sound right?
- If I need to replace the PCB on my boiler, how much should I expect to pay?
What does the FC fault code mean on my Viessmann boiler
If your Viessmann boiler is showing the FC fault code, there are a few errors that your boiler repair company are going to need to check for. The FC fault code has forced the burner in your boiler to go into fault mode.
They’ll need to check the following components:
- Gas valve
- Fan
- Flue
- PCB
In general, when a fault code is displayed, the printed circuit board (PCB) has detected an error that means your boiler isn’t working at its optimum or is potentially dangerous. For that reason, it’s likely that your boiler will lockout until the problem has been fixed.
Can the FC fault code be fixed without a boiler engineer
Some faults can easily be fixed. For instance, a boiler with low water pressure can be fixed by topping up the water in your central heating system using the external filling loop.
However, the FC fault code isn’t a simple fix. And, there’s a chance that the boiler is dangerous, which is why the boiler has locked out in the first place.
So, don’t reset your boiler to try and fix the problem. You’ll need to call an emergency boiler repair company. These companies will have Gas Safe engineers that have the qualifications and experience to fix your boiler.
They’ll be able to pinpoint which of the above components are causing the problems. And, once they’ve found and fixed the problem, they’ll reset the boiler on your behalf.
What problems can occur with the gas valve on my boiler
One of the most common culprits that causes the FC fault code to be displayed on Viessmann boilers, is the gas valve.
The gas valve controls the flow of gas into the burner. And, if it’s not operating correctly, it might be letting-by (leaking), or not providing the burner with enough gas to produce a solid flame. These issues are likely to stem from the gas valve sticking.
So, the first thing your boiler engineer needs to determine, is if the gas valve is sticking. If it’s sticking partially closed, that’s going to starve the burner of gas, causing the flame to be unstable. And on the flip-side, if it’s sticking partially open, that’s going to be leaking gas into the burner which could be dangerous.
A sticking gas valve can sometimes be freed. But, for valves that are excessively worn, it’s likely that your boiler repair company is going to suggest a replacement.
How much will a new gas valve cost to fit on my Viessmann boiler
A gas valve replacement is likely to cost around £300. That includes all parts and labour. And, whilst the job might only take one day to complete, it may take your boiler repair company a day or two to order in parts from their local supplier.
Could wiring be the issue with the gas valve on my boiler
Wiring could be the issue, and that’s the next thing for your emergency repair company to check, after they’ve determined that the valve isn’t sticking.
To operate, the gas valve needs to effectively communicate with the PCB via the wiring harness. If wiring and connections are even slightly compromised, the communication between both the PCB and gas valve is going to cause the valve to work intermittently.
Your boiler engineer will check on a visual basis for any signs of damage to wiring, repairing and replacing as necessary. They’ll also want to check that any connections that are loose, are then secured.
After a visual inspection, they’ll be able to test wires, connections and the gas valve, to check each is getting power. They’ll be able to do this using a specifically designed multi-meter.
What other issues could the gas valve have that cause the FC fault code to be displayed
To ensure that the gas valve isn’t the issue, the last thing your boiler engineer will need to check, is the valve’s adjustment. If the valve is adjusted incorrectly, it’s either going to be providing too much gas to the burner, or not enough.
If the valve needs adjusting, this can be done there and then, and won’t require your boiler repair company to replace any expensive parts.
What does the fan have to do with the FC fault code being displayed on my Viessmann boiler
Viessmann state that besides the gas valve, the FC fault code can be displayed with any issue relating to the boiler’s ability to vent, including the fan.
The fan on your boiler helps to vent dangerous gases out of the flue. It does this by creating a draft. When you turn on your boiler, you’ll hear your fan kick into life, before the burner fires up. That’s because the PCB wants to recognise the fan is operational and ready to vent these gases, before it allows the boiler to ignite.
So, if there’s a problem with the fan, the PCB recognises that the boiler isn’t safe to operate and switches the burner to fault mode.
Like the gas valve on your boiler, your repair company will need to check all wiring and connections using a multi-meter, as well as testing the fan unit for power.
They’ll want to focus their testing on the 100A cable to the fan. This is the most likely cause of the fault and can be replaced if it’s causing problems.
All being well, they’ll also want to check that the fan is set to the correct speed. If the fan isn’t spinning fast enough, the draught it creates won’t be big enough to vent gases out of the flue, and that means the boiler is dangerous.
My boiler’s fan doesn’t have power, what’s the fix
If your emergency boiler repair company has tested the fan using a multi-meter and it doesn’t have any power, unless they can repair it, it will need to be replaced.
A new fan for an average Viessmann boiler will be around £250. This will vary slightly depending on the exact model of boiler you own, and therefore, the cost of parts.
Your new fan will be replaced within one working day, subject to parts being available from a local supplier.
What is the flue, and how could this cause the FC fault code to be displayed
The flue is the large pipe that is on the exterior of your property (usually white). It will either be horizontal (coming out of the wall), or vertical (coming out of the roof).
It’s rare that a flue is going to cause the FC fault code to be displayed, but not unheard of. If there is any obstruction in flue, that’s going to reduce its ability to get gases out of your property.
If your flue is extremely old, it could have degraded to a point where it’s collapsed and essentially, blocking itself. The fix here, is a replacement flue.
A more common cause that relates to flues, is a vertical flue that’s become blocked. Vertical flues should be fitted with a flue guard. This stops things such as leaves dropping into the flue. If the problem here is a blockage, the flue needs to be removed, cleared and refitted, alongside a flue guard.
My boiler repair company thinks the PCB is causing the FC fault code to be displayed, does this sound right
Another reason the FC fault code could be displayed on your boiler, is because of a fault with the PCB.
The PCB on your boiler is the most important component. It monitors sensors to determine what components are operating and when. Based on these signals, it’s able to determine whether your boiler is operating safely.
When a problem occurs, the boiler’s PCB decides which is the most suitable fault code to be displayed, helping a boiler engineer to quickly find the problem. But, if the PCB is faulty, there’s a good chance that the fault codes being displayed are incorrect.
For instance, it might not be receiving the correct signals from the gas valve, due to a wiring fault. Whilst the PCB shows a fault code (such as FC) meaning the gas valve is the problem, the PCB could be the culprit instead.
So, as your boiler engineer did with all other electrical components so far, they’ll need to test the PCB, and all its wiring and connections. Loose connections can be secured, whereas small sections of damaged wiring can be replaced.
If I need to replace the PCB on my boiler, how much should I expect to pay
If your boiler repair company can pinpoint the boiler’s PCB as being the problem, a replacement will clear the FC fault code from the display panel.
You should expect to pay around £400-500 for a new PCB, depending on the model of boiler you have.
Other Viessmann boiler issues
For more boiler issues regarding the Viessmann Boiler then please visit the Ideal Boiler Problems And Cures page.