A21
FAULT CODE
Worcester Bosch
Thermostat / Receiver Communication Fault
Low Severity
DIY Check Possible
The boiler cannot communicate with the wireless thermostat receiver. Usually caused by low batteries in the thermostat, or the thermostat being out of range.
Step-by-Step Fix Guide
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Step 1
Replace the batteries in the wireless thermostat
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Step 2
Ensure the thermostat is within range of the receiver (typically 30m in open air)
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Step 3
Reset the thermostat and wait for it to reconnect
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Step 4
If the fault persists, call a Gas Safe engineer to check the receiver unit
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.