35 High

Atag 35 Fault Code

The Atag 35 fault code means: your boiler's internal computer has encountered a software or communication glitch and needs to be restarted.. It appears on 1 Atag model in our database.

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: Internal error
Typical repair cost £180-450 (including labour)

DIY fix possible

Press the Reset button on the control panelTurn the boiler power off at the fused spur switch for 30 secondsTurn the power back on and wait for the boiler to restart

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Atag models that show the 35 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Atag 35 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026