Weil-McLain No Heat to Distribution System

Boiler runs but radiators or baseboards stay cold

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Air locked zones, failed zone valve, circulator not running for that zone, closed isolation valve

How to Fix / Troubleshooting

Safety first: Turn off power before manually operating zone valves or bleeding air. Use caution with hot water.

  • 1. Check thermostat: Confirm the thermostat for the affected area is set to heat and above room temperature.
  • 2. Feel piping: Carefully touch the supply and return pipes for the zone near the boiler. If the supply is hot but the return is cold, flow is likely blocked.
  • 3. Zone valve check: For motorized zone valves, verify the manual lever (if present) moves freely and that the valve opens when the thermostat calls. Replace the valve head if it does not actuate.
  • 4. Bleed air from zone: Use purge valves on the return manifold to flush air from the affected loop until a steady stream of water flows.
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Repair Difficulty

Medium 3/5

Required Part

Zone Valve
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