BoilerFaultCodesWhat the manual says
Manufacturer manualExchanger protection activation – no system circulation air in system
What causes this fault?
This fault occurs when the boiler detects that heat is not being carried away from the heat exchanger fast enough, causing it to reach a dangerously high temperature. The most common reasons are a failed pump that isn't pushing water around, or a buildup of air and sludge that is blocking the flow within the pipes.
This issue is more frequent in autumn when heating systems are switched back on after a summer of inactivity, which can cause internal pump components to seize.
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.
Avoid the next call-out bill
A cover plan would handle faults like F43: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.