BoilerFaultCodesYour boiler is currently running a background check on its internal temperature readings to ensure they are accurate before it starts up.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Return temperature sensor self-test. The self-test for the return temperature sensor is activated.
What causes this fault?
This code appears when the boiler's internal computer notices a potential discrepancy between its temperature sensors and triggers a verification check to ensure the readings are safe. It usually happens because the return sensor is beginning to fail or there is a minor electrical communication issue within the internal wiring. If the test fails repeatedly, it prevents the boiler from firing up to protect the system from overheating.
DIY fix possible
Wait for 2 to 5 minutes for the test to complete automaticallyIf the code persists, try resetting the boiler using the button with the flame/cross symbolMonitor the display to see if it transitions into a normal working code like S.0 or S.4
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