BoilerFaultCodesYour boiler is performing a self-diagnostic check on its internal temperature sensors and has temporarily paused heating until it confirms everything is working correctly.
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 sensor test running, heating demands are blocked
What causes this fault?
This occurs when the boiler's control system notices an unusual discrepancy between the temperature readings of the flow and return pipes. To ensure the heat exchanger doesn't overheat, the boiler pauses operation to run a quick test and verify that the internal sensors are reporting accurate data. It is often triggered by air bubbles trapped in the system or a pump that is beginning to struggle with water circulation.
This can be more frequent in autumn when the heating is turned on for the first time after summer, as air often settles in the pipework during the warmer months.
DIY fix possible
Wait up to 15 minutes for the automated test to completeSwitch the boiler off and back on at the fused spur switch to trigger a restartEnsure all radiator valves are open to allow for proper water circulation
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