D3 218
FAULT CODE
Worcester Bosch
External Thermostat Circuit Fault
Medium Severity
Engineer Required
The wiring from the room thermostat has a fault.
Step-by-Step Fix Guide
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Step 1
Check thermostat wiring
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Step 2 Engineer only
Replace thermostat batteries if wireless
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.