Viessmann Boiler A4 Fault Code
The Viessmann fault code A4 related to an airlock in the pump or a circulation issue and here we have Q & A or require an engineer for an emergency boiler repair.
The Viessmann Boiler Fault Code A4 Error Common Q & A
Just below, we have a list of common questions relating to the a4 fault code on the Viessmann Boiler.
- What does the A4 fault code mean on my Viessmann boiler?
- Can I reset my boiler to clear the A4 fault code from the display panel?
- What should my engineer check first?
- How do I bleed radiators and towel rails?
- My pressure has dropped after bleeding radiators and towel rails, what should I do?
- After bleeding the system of air, what’s the next step to fix the A4 fault code?
- My engineer thinks my pump is faulty, is this right?
- If I need a new heating pump, how much should I expect it to cost?
- What else could affect the flow rate of my pump?
- How can heating sludge be removed from my system?
- Could an electrical issue be causing the A4 fault code to be displayed?
What does the A4 fault code mean on my Viessmann boiler
If your Viessmann boiler is showing the A4 fault code on the control panel, it means that there’s an air lock in the pump, a circulation issue meaning that optimal flow rate in your heating system isn’t being achieved.
Your boiler displays a fault code to give your heating engineer an indication of what the problem might be. In extreme circumstances, your boiler will lockout. That’s going to mean that your boiler won’t work until the problem has been fixed, and the boiler has been reset.
Can I reset my boiler to clear the A4 fault code from the display panel
You shouldn’t try to fix your boiler by resetting it. The reset function is only designed to be used once a problem has been fixed.
In this case, there’s a chance that the problem is with the pump. If you reset your boiler, tricking it into working for just a few minutes, the pump could be put under excess strain. And, that’s going to lead to the pump wearing out prematurely, and expensive repair bills.
Instead of resetting your boiler, call an emergency boiler repair company. They’ll have Gas Safe registered engineers that will be able to fix your problem. Once fixed, they’ll reset the boiler to clear the A4 fault code from the display panel.
What should my engineer check first
The first thing your boiler engineer is going to check, is the pump. It’s likely that the pump is airlocked, and this is going to act like a blockage.
After dismantling your boiler, they’ll locate the bleed screw on the pump. This allows them to bleed the air from the pump, so your pump can operate freely.
If there is air in the pump, there’s a good chance that there’s air in the rest of the heating system. They’ll bleed radiators and towel rails, although this is something you could do on a DIY basis.
If your water is of a certain quality being too black, then you could need a central heating power flush and you may need a gas safe registered engineer to do this for you.
How do I bleed radiators and towel rails
You’ll need a specifically designed radiator bleed key. The bleed key fits directly onto the bleed valve on the side of your radiator and/or towel rail. You’ll also need a container to catch water, and towels to protect carpets and walls.
Slowly open the valve, ensuring the container to catch water is located just below the valve. If there is no noise, and water starts dribbling from the valve instantly, close it; there is no air in that radiator.
If there’s air in a radiator or towel rail, you’ll hear a hissing noise. Leave the valve open until the hissing noise has stopped. The hissing noise will be replaced by water coming out of the valve. This signals that the radiator or towel rail, is now free from air.
My pressure has dropped after bleeding radiators and towel rails, what should I do
Removing airlocks can sometimes drop your boiler’s pressure. And, your boiler won’t work correctly if it’s not set to its optimum pressure. Typically, this optimum pressure is 1.3 bar (always check your owner’s manual).
If you need to top up your boiler’s pressure, you can do so, by using the filling loop. This is a braided hose that’s usually located just beneath the pressure gauge, underneath the boiler’s casing.
After topping up your boiler, if the pressure is too high, you can allow water to escape via towel rails or radiators, using the same method as you used to bleed them of air.
After bleeding the system of air, what’s the next step to fix the A4 fault code
As this is a circulation issue, the focus here, tends to be on the pump. Free of air, the next stage is to check that the pump isn’t blocked in any way.
A common blockage comes in the form of heating sludge. This is a build-up of iron oxide (rust). As sludge travels around the heating system, it breaks down to create thick and black heating water.
But, not all rust particles are broken down, and some sludge can be incredibly thick. This can easily block up the pump and cause a circulation issue.
Your boiler repair company will need to manually remove any sludge from the heating pump, ensuring that afterwards, the pump operates freely.
But, if sludge has found its way into the heating pump, it’s also in the rest of the heating system. The sludge will need to be removed to stop the same problem happening again.
My engineer thinks my pump is faulty, is this right
If your pump has been airlocked or has been blocked by heating sludge, it’s likely to have been put under excess pressure, causing it to wear out prematurely. And in many scenarios, it makes sense to replace the component, rather than fixing it.
If I need a new heating pump, how much should I expect it to cost
Conent
The cost of a new heating pump is going to vary depending on the size pump your need. A typical pump replacement, using a leading pump brand such as Grundfos, is going to be around £250 including parts and labour; the job is likely to take one working day to complete.
What else could affect the flow rate of my pump
The flow rate of your pump is essential to ensure that hot water is delivered at the right temperature. So, before jumping to conclusions, your boiler engineer will want to check the flow rate setting on the pump.
Most modern pumps will have multiple settings; typically, three. If the flow rate on your pump is too low, that’s going to restrict its ability to circulate water around your heating system.
Adjusting the flow rate is a job for a Gas Safe engineer, simply because the boiler will need to be dismantled. However, it’s not a big or expensive job.
How can heating sludge be removed from my system
The best way to stop heating sludge blocking up boiler components in the future, is to start by flushing out the system.
Your boiler engineer will hot flush the system using cleaning chemicals. For newer systems, a power flush can be used. This is a hot flush at pressure. This isn’t advisable for older systems, as it can easily cause leaks.
After circulating chemicals throughout the heating system for a while, the dirty water can be drained, taking heating sludge with it.
Once drained, the system needs to be refilled with not just water, but central heating inhibitor too. Central heating inhibitor breaks down heating sludge into small particles, that are a lot less likely to get lodged in components such as the pump.
But, this broken down heating sludge does need to be removed from the system. This can be done by fitting a magnetic system filter. This catches most of the heating sludge, and the filter can be removed and cleaned with your annual boiler service.
Could an electrical issue be causing the A4 fault code to be displayed
With any fault code, a communication error between components could be the issue. It’s the printed circuit (PCB) that gives and receives signals from all components in your boiler.
It gives signals for components to start up and shut down. And, it receives signals to ensure these components are doing what they should be. When they don’t, it will lock out and display a fault code.
In the case of the A4 fault code, it could be that the wiring between the pump and the main PCB is defective. So, although the pump is circulating correctly, the PCB isn’t recognising it. Likewise, the NTC thermistors that monitor the flow and return temperature of water also could be the issue.
Your boiler engineer will want to use a multi-meter to test all these electrical components, replacing any offenders.
Other Viessmann boiler issues
For more boiler issues regarding the Viessmann Boiler then please visit the Ideal Boiler Problems And Cures page.