D.9 Low
Your boiler is receiving a instruction to heat water to a specific temperature from an external thermostat or smart heating control.
Technical description: Flow target temperature from external analogue regulator terminal
Typical repair cost: £0-80 (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 D.9 — 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
- External control wiring
- Thermostat
*Affiliate links — we may earn a commission at no extra cost to you.