What the manual says
Manufacturer manualThe 'OVERHEAT' red indicator on the control panel will flash indicating that the overheat thermostat has operated. This will automatically switch off the boiler in the case of a control malfunction causing overheating.
From this model's manual
Verified against the Grant/Grant Vortex Eco installation & service 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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All 53 fault codes on the Vortex Eco
Seeing a different code? Every code this model can display, in one place.
10121821.02226.0313636.04454616992116143198232286348396429594727728729A1.2A1.3A2.2A3.2Blinking REDBurner lock-outConstant REDDHW PUMP indicator FLASHINGFast flashFlashes redFlashes red/greenGREENGREEN blinkingLED offLock-outLockoutLOW PRESSUREOFFORANGEORANGE blinkingOverheat thermostatREDRED blinkingRED fast blinkingRED steady ONSlow flash