High Lockout
A8 on Worcester Bosch Greenstar CDi Compact

Your boiler has lost its connection with the thermostat, meaning they are no longer speaking to each other to control your heating.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Communication to the thermostat interrupted

What causes this fault?

This fault occurs when the wireless link between your boiler and your wall thermostat is broken, preventing the boiler from receiving instructions to turn on. The most common reasons are dead batteries in the thermostat unit or an obstruction like a new piece of metal furniture blocking the radio signal between the devices.

This issue often appears at the start of autumn when homeowners try to turn their heating on for the first time in months, only to find the thermostat batteries have drained over the summer.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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