High
43 on Johnson Starley C10d

Your boiler's internal thermometer has developed an electrical fault, meaning the system can no longer safely monitor how much heat is returning to the unit.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Return air temperature short circuit. Temperature sensor shorted to earth. Check wiring connections not shorting to earth. Check sensor resistance.

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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