BoilerFaultCodesTechnical description
ALTERNATING 'H' 'E' GO TO FRAME 86
What causes this fault?
This fault occurs when the water within the boiler exceeds a safe temperature limit, triggering a safety shut-off to protect the internal components. It is physically caused by a lack of water flow, often due to a broken internal pump or a blockage in the pipework that prevents heat from being carried away. In some cases, a faulty sensor may be incorrectly reporting that the system is overheating when it is actually at a normal temperature.
This issue often surfaces during the first few cold days of autumn when the central heating is turned back on after being idle all summer, which can cause the pump to become stuck.
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.