High
A08 on Vokera Vision Combi 25C / 30C

Your boiler has detected that the water temperature coming back into the unit is being read incorrectly or is running hotter than it should be, causing the system to stop working safely.

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 thermistor fault / Return thermistor over temperature / Temperature differential inverted

From this model's manual
Verified against the Vokera Vision Combi 25c 30c installation & service manual, page 9.
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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