BoilerFaultCodesYour boiler is struggling to accurately measure the temperature of your hot water, which typically means your taps will only run cold or have inconsistent heat.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Insecure electrical connection, incorrect resistance values (9.7-10.3 kΩ at 25°C), or lack of continuity between the PCB and the thermistor.
What causes this fault?
This fault occurs when the internal sensor responsible for monitoring hot water temperature starts sending incorrect signals to the main control board. The most common reason is that the sensor's internal components have degraded over time or a wire has shaken loose, leaving the boiler unable to tell how hot the water actually is. As a safety precaution, the boiler will stop heating the water to prevent it from reaching dangerous temperatures.
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 DHW Thermistor Fault — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.