BoilerFaultCodesYour boiler has detected that either a temperature sensor in the exhaust pipe is faulty or the main heating component is becoming blocked and dirty.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue thermistor fault or heat exchanger needs cleaning
What causes this fault?
This fault occurs when the internal safety sensors detect that the exhaust gases are becoming too hot, which is often a sign that heat isn't being transferred efficiently to your water. The most common reason is a buildup of debris and carbon deposits inside the main heat exchanger, which restricts airflow and causes the unit to overheat. In some cases, the sensor itself may have simply failed or developed a loose connection, sending an incorrect reading to the control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E09 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Vokera Mynute Vhe is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.