Vokera E070 Fault Code: Causes, Fixes & Repair Costs
What does the Vokera E070 fault code mean?
The E070 fault code appears on Vokera Vision Plus series boilers and indicates a problem with the flue thermistor — the temperature sensor responsible for monitoring the exhaust gases as they leave the boiler through the flue. When this sensor returns an abnormal reading, or stops responding altogether, the boiler locks out as a precautionary safety measure to prevent the appliance from running in a potentially unsafe condition. The thermistor itself may have failed, its wiring may be compromised, or the flue may be partially blocked — causing exhaust temperatures to behave unexpectedly. Because this is a lockout fault on the Vision Plus, Vokera's own guidance states that all E-prefix faults (except E040 and E041) require an engineer to attend rather than simply resetting the boiler yourself.
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 degraded flue thermistor (NTC sensor) Common
The flue thermistor is an NTC (negative temperature coefficient) sensor that changes its electrical resistance in response to temperature. Over time these sensors drift out of tolerance or fail outright, sending incorrect resistance values back to the PCB. When the board can no longer make sense of the reading, it triggers E070. This is the single most common cause of this code.
- Wiring fault or corroded connections at the sensor Common
Even if the thermistor itself is fine, loose connector pins, chafed cable insulation, or corrosion on the sensor plug can break or distort the signal reaching the PCB. The board interprets this as a sensor fault and locks the boiler out. Damp conditions inside the casing — sometimes caused by a small internal leak — accelerate corrosion.
- Blocked or obstructed flue outlet Sometimes
A partial blockage in the flue — caused by debris, leaves, a bird's nest, or even heavy snowfall — can cause exhaust gases to back up and heat the flue thermistor beyond its expected range. The boiler interprets this as an abnormal temperature event and shuts down. A visible external check of the flue terminal is the one action a homeowner can safely carry out.
- PCB fault Rare
If the sensor and all associated wiring test within spec, the control board itself may be misreading the incoming signal. PCB faults can arise from component ageing, moisture ingress, or electrical surges. An engineer can test the board with a multimeter; repair is sometimes possible, but replacement is often needed.
How to fix it
- Check the flue terminal externally for obvious blockages DIY safe
Go outside and visually inspect where the flue exits the building. Look for any debris, vegetation, ice, or a bird's nest blocking the outlet. Do not attempt to access the flue pipe itself — just check the visible terminal. Clear any loose surface debris if it is safely accessible from ground level.
- Attempt a single boiler reset DIY safe
On the Vision Plus, turn the mode selector to the OFF/RESET position and then immediately back to your preferred operating mode (heating and hot water, or hot water only). Alternatively, press and hold the reset button for 3–5 seconds. If the boiler fires up and runs normally, monitor it over the next hour. Do not repeat the reset more than once or twice — repeated resets on a locked-out boiler can mask a developing safety issue.
- Contact a Gas Safe registered engineer to test the flue thermistor Gas Safe engineer
The engineer will use a multimeter to measure the resistance of the NTC thermistor across its operating temperature range and compare the reading against the manufacturer's specification. If the sensor is out of tolerance or open-circuit, it will be replaced. The thermistor itself is inexpensive (typically under £30 for the part), making this a relatively low-cost fix when it is the root cause.
- Have the engineer inspect and clear the flue system Gas Safe engineer
The engineer will check the full flue run — including bends, terminal, and condensate drain if applicable — for partial blockages, damage, or incorrect installation that could be causing exhaust back-pressure. Any obstructions will be cleared and the flue integrity confirmed.
- Have the engineer check wiring and connector integrity Gas Safe engineer
All wiring back to the sensor connector and onward to the PCB will be inspected for signs of corrosion, chafing, or loose terminals. Faulty connections will be repaired or the loom replaced as needed. This step is often carried out at the same time as thermistor testing.
- Ask the engineer to assess the PCB if other causes have been ruled out Gas Safe engineer
If the thermistor and all wiring test correctly, the PCB may be generating or misreading the fault. The engineer can test the relevant PCB terminals. On an older Vokera boiler, weigh the cost of PCB replacement (which can run to several hundred pounds) against the age of the appliance before proceeding.
Parts you may need
- Flue NTC thermistor sensor · from £25
- Sensor wiring harness / connector loom · from £35
- Flue terminal (horizontal, standard) · from £45
- PCB (Vision Plus control board) · from £220
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 £120–£320, depending on the underlying cause.
Frequently asked questions
Can I just keep resetting the E070 code to get my heating back on?
We strongly advise against it. Vokera's own guidance for the Vision Plus states that E-prefix lockout faults (other than E040 and E041) need an engineer, not repeated resets. The boiler has locked out because the flue thermistor is sending a signal outside safe parameters. Running through multiple resets could allow the boiler to fire when the exhaust temperature monitoring is compromised, which is a safety risk. One careful reset attempt is reasonable; after that, call a Gas Safe engineer.
How much does it cost to fix a Vokera E070 fault?
If the flue thermistor is the culprit — which is the most common cause — you are typically looking at £120–£320 all-in for diagnosis, the part (under £30), and labour. If wiring repairs are also needed, costs sit toward the upper end of that range. A PCB replacement is a much bigger job and can cost £350–£550 or more for parts and labour; on an older Vokera boiler it is worth discussing with your engineer whether a replacement boiler makes more financial sense at that point.
What is the flue thermistor and why does it matter?
The flue thermistor is a small NTC (negative temperature coefficient) sensor mounted in or near the flue. It continuously measures the temperature of the exhaust gases leaving the boiler. If gases get too hot — suggesting a blockage or combustion problem — or if the sensor stops reporting altogether, the boiler's PCB locks the unit out to prevent unsafe operation. It is a key part of the boiler's built-in safety system.
Will an annual boiler service help prevent the E070 code from coming back?
Yes. During a service a Gas Safe engineer will inspect the flue, check sensor readings, clean components, and spot early signs of wiring corrosion or sensor drift before they trigger a lockout. A Vokera service typically costs £70–£140 and is the single most effective way to catch flue thermistor issues — and many other fault codes — before they leave you without heating or hot water.