Vokera Boiler A07 Fault Code
The Vokera fault code A07 NTC thermistor problem Q & A or require an engineer for an emergency boiler repair.
The Vokera Boiler Fault Code A07 Error Common Q&A
Just below, we have a list of common questions relating to the A07 fault code on the Vokera boiler.
- What does the A07 fault code mean on my Vokera boiler?
- What are NTC thermistors on boilers?
- Why does my boiler lockout when there’s a problem with the thermistor?
- What’s causing the problem with the NTC flow thermistor on my Vokera boiler??
- What is scale, and how can it lead to the A07 fault code being displayed on my Vokera boiler?
- Can scale problems be fixed?
- How do blockages and air locks occur in a heating system?
- How can blockages and air locks lead to the A07 fault code being displayed on my Vokera boiler?
- How can blockages and air locks be fixed to clear the A07 fault code?
- My boiler engineer thinks there’s scale build-up on the heat exchanger, can this be fixed?
- How much does it cost to replace the heat exchanger on my Vokera boiler?
- What could cause an inaccurate temperature reading, and the A07 fault to be displayed?
- How could the PCB be at fault?
- How will checking the PCB with a multi-meter help determine the fault?
- What happens when there’s water damage in a boiler?
- If it’s the PCB unit that’s to blame, how much will that cost to fix?
What does the A07 fault code mean on my Vokera boiler?
If your Vokera boiler is showing the A07 fault code on the display panel, it means there is a problem with the NTC thermistor on the flow side of the boiler.
The temperature of the water leaving the boiler is too high.
What are NTC thermistors on boilers?
The NTC thermistor is a device that monitors the temperature of water around the heating system.
Boilers have an NTC thermistor fitted on the flow side (hot water coming out of the boiler) and the return side (water returning to the boiler from the heating system).
The NTC thermistors measure in resistance. As temperature goes up, the resistance reading will go down.
This reading is then fed back to the boiler’s printed circuit board (PCB).
Why does my boiler lockout when there’s a problem with the thermistor?
If the PCB recognises that the NTC thermistors (and therefore, heating water) are above or below temperature it will lock out.
Overheating can cause problems to expensive parts such as the heat exchanger. By locking out the boiler, these parts are protected.
What’s causing the problem with the NTC flow thermistor on my Vokera boiler?
There are a range of potential causes that could lead to the fault, including:
- Scale build-up around the NTC flow thermistor
- Blockage or air lock in the heating system
- Scale build-up in the heat exchanger
- Inaccurate temperature monitoring
- Main PCB fault
What is scale, and how can it lead to the A07 fault code being displayed on my Vokera boiler?
Scale comes from natural mineral deposits in water. Like dishwashers, boilers can get clogged up with scale and the internal components will slowly deteriorate.
NTC thermistors take a reading from the section of pipe they’re fitted too, rather than the average water temperature of the whole heating system.
Unfortunately, if scale builds up near these NTC thermistors, the reading will be much higher than it should be. This is because scale that attaches it to pipework or the NTC thermistor will burn hotter than the average temperature of the heating water.
This leads to an incorrect reading being fed back to the PCB. The PCB thinks the boiler is overheating water and locks out to prevent damage to boiler parts.
Can scale problems be fixed?
Lots of brands offer products such as “noise reducers” and descalers. Sentinel and Fernox are two good examples.
If the scale problem isn’t serious, a boiler engineer will be able to dose the system with this fluid. This will break down the scale, which can then be caught by a scale reducing filter.
However, if the problem is serious, it may be that sections of pipework or the NTC thermistor need to be replaced to solve the problem.
How do blockages and air locks occur in a heating system?
Blockages typically come from heating sludge. This is a build-up of rust and grime that breaks off from the inside of radiators and pipework.
But air locks usually occur when a system is refilled. For instance, if a heating engineer has fitted a radiator they would’ve had to drain the system and refill it. The system should then be bled.
However, small leaks in a heating system can lead to ongoing air locks.
How can blockages and air locks lead to the A07 fault code being displayed on my Vokera boiler?
When air locks and blockages are to blame, it’s likely the boiler is suffering from a circulation fault.
If the heating system is blocked or air locked (specifically, the heating pump), then there won’t be sufficient water circulation.
That will lead to the heat exchanger overheating. The boiler will lock out, as any overheat on the heat exchanger could lead to cracks and an expensive repair bill.
How can blockages and air locks be fixed to clear the A07 fault code?
For airlocks, a heating engineer will be able to bleed all radiators and towel rails. They’ll also need to bleed the pump.
As this involves removing the boiler casing, only Gas Safe qualified engineers should complete this job.
Blockages that have been caused by heating sludge can be cleared if they are small. And the easiest way is to dose the system with central heating inhibitor and install a magnetic system filter. Inhibitor breaks down rust, rather than descaler that breaks down scale.
The boiler engineer will flush the system through to clear most of the debris. Debris that breaks off further down the line will now be caught by the magnetic system filter.
Remember, get your heating engineer to clean out this filter with every boiler service, as once they fill up your boiler is left unprotected.
My boiler engineer thinks there’s scale build-up on the heat exchanger, can this be fixed?
If there’s a build-up of scale on the heat exchanger, this can be removed manually.
However, what a boiler engineer needs to look out for is that there are not any small cracks in the heat exchanger itself.
As we mentioned with the NTC thermistor overheating, scale creates hotspots on the heat exchanger too, not just pipework. When it does, this can weaken the exchanger plate and cause cracks.
Eventually, these cracks form leaks, and that can lead to lots of damage to electrical components.
If this is the case, the heat exchanger will need to be replaced to fix the problem.
How much does it cost to replace the heat exchanger on my Vokera boiler?
The cost will vary considerably depending on the model of Vokera you have.
Expect to pay somewhere in the region of £400-500 for a replacement heat exchanger for popular models.
What could cause an inaccurate temperature reading, and the A07 fault to be displayed?
If there’s an inaccurate resistance reading being fed back to the PCB, there’s a good chance that the NTC thermistor itself is to blame.
Replacements are cheap. You could be paying as little as £20 for parts, and a few hours labour including the diagnostic and installation.
So, there’s little point spending time trying to clean or fix the one that’s currently fitted.
How could the PCB be at fault?
The PCB is the most important part in the boiler. It sends and receives signals to all electrical components in the appliance.
A typical example is the one mentioned here, whereby it receives temperature readings from the NTC thermistors.
But, it’s also connected to components such as the pump, gas valve and diverter valve. When there’s a problem with an electrical component, the PCB needs to be ruled out as a culprit.
To rule out the PCB as the problem, the boiler engineer will need to:
- Check the connections to and from the PCB using a multi-meter
- Complete a visual inspection for water damage
How will checking the PCB with a multi-meter help determine the fault?
The smallest issue with wiring or connections (such as them being partly loose, or damaged), could interfere with how the PCB works.
Checking the PCB with a multi-meter will help to determine if there’s a problem. And if there is a problem, the multi-meter helps to locate where it is.
What happens when there’s water damage in a boiler?
Water damage can come from various components. However, if there’s a NTC flow thermistor overheat fault code being shown, it’s likely that the heat exchanger is to blame.
The boiler engineer will need to check not just the components that are leaking, but what they’ve leaked onto.
Water damage can sometimes completely ruin a boiler. So, they’ll need to check each expensive component before replacing anything.
There’s little point replacing multiple expensive components, when that money could be going towards the cost of a new boiler.
If it’s the PCB unit that’s to blame, how much will that cost to fix?
Expect to pay upwards of £400 for a PCB replacement.
The diagnostic plus installation, will take around 1 day.
Other Vokera boiler issues
For more boiler issues regarding the Vokera then please visit the Vokera Boiler Problems And Cures page.