F12 Medium
Your boiler has lost its connection to the sensor that monitors your hot water temperature, which means you will likely experience cold showers until it is fixed.
Technical description: Domestic hot water (DHW) sensor fault – sensor damaged, wiring shorted or wiring disconnected – check the wiring
Typical repair cost: £90-160 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F12 — no call-out fees, no surprises.
*Affiliate links — we may earn a commission at no extra cost to you. Prices shown are starting prices.
Parts commonly replaced
- DHW Temperature Sensor (NTC)
- Wiring harness connector
*Affiliate links — we may earn a commission at no extra cost to you.