Vokera E065 Fault Code: Causes, Fixes & Repair Costs
What does the Vokera E065 fault code mean?
The E065 code on a Vokera boiler signals a problem with the flue thermistor — the sensor responsible for monitoring the temperature of exhaust gases as they leave the boiler through the flue. When this sensor detects an abnormal reading, reads outside its expected range, or fails entirely, the boiler locks out as a precaution to prevent unsafe operation. In short, the boiler cannot confirm that flue gases are being expelled safely, so it shuts itself down until the issue is investigated. This fault appears across several Vokera E-series models and should be treated as a safety-related lockout rather than a minor nuisance.
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
- Faulty or failed flue thermistor Common
The flue thermistor itself is the most frequent culprit. Over time the sensor degrades, giving readings that are out of range or no signal at all. The boiler's control board detects this and triggers the lockout. Replacement of the sensor by a Gas Safe engineer usually resolves the fault quickly.
- Blocked or partially obstructed flue terminal Common
Leaves, bird nesting material, ice, or compacted snow at the flue outlet can restrict airflow and cause flue gas temperatures to rise abnormally or fluctuate, triggering the thermistor fault. This is particularly common in autumn and winter. A visual check of the external terminal is something a homeowner can safely do.
- Loose, damaged, or corroded wiring connections Sometimes
The wiring between the flue thermistor and the PCB can suffer from corrosion, vibration-related loosening, or physical damage over time. A poor connection produces an intermittent or incorrect signal that the board interprets as a sensor fault. An engineer will check continuity and resistance through the circuit.
- PCB misinterpreting the thermistor signal Rare
If the thermistor tests within specification but the fault persists, the PCB itself may be at fault — either misreading the sensor input or suffering from an internal component failure. Because PCB replacement is costly, engineers will typically rule out all other causes first.
How to fix it
- Visually inspect the external flue terminal for blockages DIY safe
Go outside and look at where the flue exits the building. Check for leaves, debris, bird nests, ice, or anything else restricting the opening. Do not attempt to dismantle any part of the flue — a visual inspection only. If you spot an obvious blockage, remove it carefully if it is accessible without tools.
- Reset the boiler once or twice DIY safe
After clearing any visible obstruction, attempt a boiler reset. On most Vokera models this means pressing and holding the reset button (marked R or a flame symbol with a line through it) for around 3–5 seconds until the display clears. On some dial-controlled models, turn the selector to the reset or OFF/RESET position and hold briefly. Attempt this no more than two to three times. If the E065 code returns promptly, repeated resetting will not fix the underlying problem and may mask a safety issue.
- Check system pressure is within normal range DIY safe
While you have the boiler in view, glance at the pressure gauge. A healthy reading is typically between 1 and 1.5 bar when the system is cold. If pressure has dropped below 0.8 bar, top it up via the filling loop. Low pressure alone will not cause E065, but ruling it out avoids a second call-out.
- Call a Gas Safe registered engineer to test the flue thermistor Gas Safe engineer
A qualified engineer will use a multimeter to measure the thermistor's resistance across its operating temperature range and compare it against the manufacturer's specification. If the sensor is out of tolerance, it will be replaced. This is the most common resolution for E065 and is not something a homeowner should attempt given it involves accessing internal flue components.
- Engineer to inspect flue wiring and connections Gas Safe engineer
If the thermistor tests within specification, the engineer will trace the wiring loom from the sensor back to the PCB, checking for corroded terminals, chafed insulation, or loose plugs. A damaged wire or connector can produce the same fault signal as a failed sensor.
- Engineer to assess the PCB if all other checks pass Gas Safe engineer
Should the thermistor and wiring both prove sound, the PCB becomes the likely cause. The engineer may carry out further diagnostic checks or swap the board. Given PCB replacement costs (typically £450–£550 for parts and labour), the engineer should discuss whether repair or boiler replacement makes better financial sense for the age and condition of the appliance.
Parts you may need
- Flue thermistor / flue temperature sensor · from £35
- Thermistor wiring harness / loom · from £25
- PCB (printed circuit 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–£300, depending on the underlying cause.
Frequently asked questions
Is it safe to keep resetting my Vokera boiler when E065 appears?
No. One or two resets are reasonable to see whether a transient issue such as a momentary temperature spike has cleared. However, E065 is a safety lockout related to flue gas monitoring. If the code keeps returning, the boiler is telling you something is genuinely wrong. Repeatedly resetting it without fixing the root cause risks operating the boiler in an unsafe condition. Call a Gas Safe engineer if the fault comes back after your first couple of attempts.
How much does it typically cost to fix the Vokera E065 fault?
For the most common repair — replacing the flue thermistor — expect to pay roughly £120 to £300 including parts, labour, and a call-out fee. If the fault turns out to be a wiring issue, costs are similar or slightly lower. If the PCB is ultimately to blame, replacement can cost £450–£550 in parts and labour alone, at which point it is worth asking your engineer whether the age of the boiler makes a new installation a more sensible investment.
Can a blocked flue really cause E065?
Yes. If the flue terminal is obstructed — by leaves, a bird nest, ice, or compacted snow — exhaust gases cannot escape efficiently and flue temperatures can rise or fluctuate in ways that trigger the thermistor fault. Always start by checking the external flue outlet visually. This is one of the few checks a homeowner can safely carry out without a Gas Safe engineer, and it costs nothing.
How can I prevent the E065 fault from recurring?
Annual servicing by a Gas Safe registered engineer is the single most effective preventive measure. During a service the engineer will check thermistor readings, inspect wiring connections, and confirm flue integrity before a small problem becomes a lockout. Keeping the external flue terminal clear of debris — particularly in autumn and winter — also reduces the risk of blockage-related faults.