Vokera 07 Fault Code: Causes, Fixes & Repair Costs
What does the Vokera 07 fault code mean?
Fault code 07 on a Vokera boiler — also shown as A07 or E07 depending on the model — indicates a problem with the primary flow NTC thermistor circuit. The boiler monitors the temperature of water leaving the heat exchanger via this sensor; when the circuit appears open (i.e. no valid resistance signal is received), the boiler locks out for safety. In plain terms, the boiler either cannot read the flow temperature at all, or the reading it receives is outside the expected range. Because the sensor sits on the right-hand side of the main heat exchanger and should measure roughly 12 kΩ resistance at 20°C room temperature, any break in the circuit — whether from a failed sensor, damaged wiring, or poor circulation causing genuine overheating — will trigger this lockout. Note: this fault relates to the central heating flow sensor, not the domestic hot water thermistor.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Failed or open-circuit flow thermistor Common
The most frequent cause. The NTC thermistor on the primary flow side has either failed internally or developed an open circuit, meaning it can no longer pass a valid resistance signal to the PCB. The boiler locks out immediately as a safety precaution. Replacing the sensor is usually the fix.
- Loose or damaged thermistor wiring Common
The wiring loom connecting the thermistor to the PCB can suffer from loose plug connections, corrosion at the terminals, or chafing that breaks the circuit. This can mimic a dead thermistor and must be checked before replacing the part.
- Circulation problem causing genuine overheating Sometimes
A failing circulating pump or a heavily sludged heating system can restrict water flow through the heat exchanger. Without adequate flow, temperatures rise rapidly and the thermistor circuit reaches its upper limit. Sludge build-up is a particularly common underlying cause in older systems that have never been flushed or treated with inhibitor.
- Airlock in the primary circuit Sometimes
Air trapped in the heat exchanger or pump reduces water circulation, causing localised overheating. The boiler registers an abnormal temperature condition on the flow sensor and shuts down. Airlocks often develop after a pressure loss event or recent system work.
- Faulty PCB Rare
If the PCB cannot correctly interpret the resistance signal from the thermistor — due to moisture ingress, vibration-induced solder joint failure, or a damaged input channel — it may falsely report an open-circuit condition even when the thermistor itself is fine. This is typically only confirmed after all other causes have been ruled out.
How to fix it
- Check the boiler has power and controls are set correctly DIY safe
Verify the fused spur is switched on, the programmer or timer is set to a heating period, and any room thermostat is calling for heat above the current room temperature. These basic checks rule out a controls issue before assuming the boiler is faulty.
- Check the system pressure DIY safe
With the boiler cold, look at the pressure gauge. Most Vokera boilers should read between 1.0 and 1.5 bar at rest. If it is below 0.8 bar, top up via the filling loop following your boiler manual. Low pressure can contribute to poor circulation and overheating faults.
- Reset the boiler once DIY safe
Press and hold the reset button (usually labelled R) for 3–5 seconds until the fault code clears and the boiler attempts to restart. If it fires up and runs normally, monitor it closely. If the A07 code returns — do not keep resetting. Repeated resets will not repair a failed sensor or circulation fault and may mask a more serious overheating problem.
- Engineer to test the flow thermistor and its wiring Gas Safe engineer
A Gas Safe engineer will remove the boiler casing and measure the resistance of the flow thermistor with a multimeter (expecting approximately 12 kΩ at 20°C). They will also inspect the wiring loom, check terminal connections, and look for any signs of moisture or corrosion on the plug.
- Engineer to replace the flow NTC thermistor if faulty Gas Safe engineer
If the thermistor reads out of range or shows an open circuit, the engineer will fit a replacement Vokera-compatible NTC sensor. This is the most common resolution for fault code 07 and is a straightforward repair on most Vokera models.
- Engineer to assess and restore heating circulation Gas Safe engineer
If the thermistor tests as good, the engineer will check the circulating pump for correct operation and inspect the system for sludge or airlocks. Bleeding the pump requires removal of the boiler casing and must only be done by a qualified engineer. A power flush or a dose of central heating inhibitor combined with a magnetic filter may be recommended to address sludge.
- Engineer to evaluate the PCB if all other components test correctly Gas Safe engineer
As a last resort, the engineer will test the PCB's thermistor input channel. Loose solder joints or moisture damage may be repairable; otherwise the PCB will need replacement. An engineer may also advise on whether the overall age and condition of the boiler makes replacement a better investment than a costly PCB repair.
- Call a Gas Safe registered engineer if the fault persists or returns Gas Safe engineer
If fault code 07 reappears after a reset, or you are unsure of any of the above, contact a Gas Safe registered engineer. You can verify registration at gassaferegister.co.uk. Do not continue operating a boiler that is locking out repeatedly on a temperature fault.
Parts you may need
- Vokera NTC flow thermistor sensor · from £25
- Thermistor wiring loom / harness · from £30
- Circulating pump (Vokera compatible) · from £85
- Magnetic system filter (e.g. Fernox TF1 or equivalent) · from £55
- PCB (model-dependent) · from £280
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £100–£300, depending on the underlying cause.
Frequently asked questions
Can I fix Vokera fault code 07 myself?
The one safe DIY step is a single reset — hold the reset button for 3–5 seconds. If the fault clears and the boiler stays on, great; keep an eye on it. If A07 returns, stop resetting and call a Gas Safe engineer. The thermistor, wiring, pump, and PCB all sit inside the boiler casing and must only be accessed by a qualified professional.
How much does it cost to fix a Vokera A07 fault code in the UK?
For most homeowners, the repair is a flow thermistor replacement plus a call-out, typically coming to around £100–£200 all in. If circulation problems are found — a sludged system or failing pump — costs can rise to £250–£300 once a flush and new pump are factored in. In rare cases where the PCB or heat exchanger needs replacement, the bill can be significantly higher; a heat exchanger on a popular Vokera model typically runs to £400–£500, and a PCB can be around £280–£350 for the part alone. If facing those larger repairs on an older boiler, it is worth getting a new boiler quote for comparison.
Why does my Vokera boiler keep showing A07 after I reset it?
A persistent A07 means the underlying fault — most likely a failed thermistor or a circulation problem — has not been resolved. The reset simply clears the lockout display; it does not repair the sensor or clear sludge from the system. Repeated resets on an overheating fault can damage the heat exchanger. Book an engineer to diagnose the root cause properly.
Will an annual boiler service help prevent fault code 07?
Yes. A service typically costs £70–£100 and includes checking sensor resistances, inspecting the wiring, and assessing system water condition. Keeping the system dosed with corrosion inhibitor and fitting a magnetic sludge filter significantly reduces the risk of circulation-related faults that can trigger A07. It also means small issues — like a thermistor drifting out of range — are caught before they cause a breakdown.