BoilerFaultCodesYour heating hasn't come on because your wall thermostat has run out of power and cannot send a signal to the boiler.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Check room thermostat batteries
What causes this fault?
This fault occurs when the wireless connection between your wall thermostat and the boiler is broken because the transmitter has lost power. Without charged batteries, the thermostat cannot tell the boiler to turn on, leading the system to assume there is a communication error. The most common reason is simply that the batteries have reached the end of their life and need replacing to restore the signal.
This issue is frequently seen at the start of autumn when homeowners turn their heating back on for the first time and discover the batteries have drained over the summer months.
DIY fix possible
Locate your wall-mounted room thermostat or portable controller.Remove the battery compartment cover.Replace the old batteries with a new set of high-quality alkaline batteries (usually AA or AAA).Check if the display turns on and wait a few minutes for it to reconnect to the boiler.
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 Room Thermostat 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.