Radiators heat unevenly, some remain cold even though furnace is running normally

Safety: Allow radiators to cool before working on valves.

• Open valves: Ensure both flow and return valves on each radiator are open.
• Bleed radiators: Remove trapped air from cold radiators.
• Clean filter: If a Baxi magnetic filter is installed, isolate and clean it thoroughly.
• Balance system: Throttle back lockshield valves on radiators that heat quickly to encourage flow to colder radiators.