Fixing Baseboard Heaters That Won't Heat

Radiators are simple machines, but they rely on a delicate balance of water pressure and temperature to work effectively. When a baseboard unit stays cold while others in your home are toasty, you are likely dealing with an air bubble caught in the loop. This pocket of air prevents the hot water from circulating through the fins, leaving your room shivering while the furnace works overtime. Restoring heat is a manageable task if you follow the flow of the system. You will need to locate the bleed valve, purge the trapped air, and ensure your thermostat is communicating properly with the zone valve. A job done well results in a silent, consistent warmth radiating from the metal fins, with no gurgling sounds or cold spots to speak of.

  1. Verify System Is Running. Ensure your thermostat is set to 'heat' and the temperature is at least five degrees higher than the current room reading. Verify that the system is actually clicking on and that other heaters in the house are functioning.
  2. Find the Bleed Valve. Remove the front cover of the cold baseboard unit to expose the copper pipe and the radiator fins. Find the small valve, usually located at the end of the unit near the top pipe.
  3. Release Trapped Air. Hold a cup or rag under the bleed valve. Use a radiator key or flathead screwdriver to slowly turn the valve counter-clockwise until you hear a hissing sound of escaping air.
  4. Check Zone Valve Function. Go to the boiler area and find the zone valves. If the unit remains cold, check if the actuator on the zone valve is manually engaged or showing a 'power' light when the thermostat calls for heat.
  5. Unblock the Damper Flap. Check the metal damper flap along the top of the heater to ensure it is in the open position. Sometimes these get knocked shut, physically blocking the rising heat from entering the room.
  6. Confirm Heat Restoration. Turn your thermostat back to the desired temperature and wait twenty minutes for the water to cycle through the loop. Feel the pipe near the bleed valve to confirm it is becoming hot to the touch.