Boiler shows A07, heating stops, flow temperature rises rapidly

Safety: Allow the boiler and system to cool before touching any valves or pipework.

• Check system valves: Confirm that the boiler flow and return isolation valves are fully open (usually slot in line with the pipe).
• Verify radiator valves: Ensure enough radiators are open to allow proper circulation.
• Check system filter: If a magnetic or dirt separator is installed on the return, inspect its service indicator. Have it cleaned by a competent person if heavily contaminated.
• Listen for pump operation: When the boiler starts, you should hear or feel the pump running. If it is silent or excessively hot, it may be stuck.
• Technician tasks: A heating engineer can free or replace the pump, flush the system, and clean the primary heat exchanger if required.