BoilerFaultCodesYour boiler has stopped working because an internal temperature sensor that monitors your hot water or heating has developed an electrical fault.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: S3 sensor short circuit
What causes this fault?
This fault occurs when the boiler's control board detects an incorrect electrical signal from the temperature sensor, indicating a short circuit. The most common reason is that the internal components of the sensor have failed due to age, or moisture has compromised the electrical connections. Without an accurate temperature reading, the boiler shuts down as a safety precaution to prevent overheating.
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 F05 — 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.