High
43 on Johnson Starley C16d

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the air returning to the unit, causing it to shut down for safety.

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.

What the manual says

Manufacturer manual

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

From this model's manual
Verified against the Johnson Starley C16d installation & service manual, page 28.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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