Cylinder Thermistor Fault Medium

Keston Cylinder Thermistor Fault Fault Code

Also written as CYLINDERTHERMISTORFAULT — same fault.

The Keston Cylinder Thermistor Fault fault code means: your boiler has lost the signal from the sensor that monitors the temperature of your hot water cylinder, meaning it does not know when your water is hot enough.. It appears on 1 Keston model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Check Cylinder Thermistor Wiring, Check Cylinder Thmr
Typical repair cost £120-200 (including labour)

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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Cylinder Thermistor Fault: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Keston models that show the Cylinder Thermistor Fault fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Keston Cylinder Thermistor Fault fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026