Weil-McLain
Boiler Fails to Shut Off on Temperature
Boiler runs continuously and overshoots thermostat setting
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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
Stuck relay on control board, thermostat wiring shorted, miswired zone control, sensor out of calibration
How to Fix / Troubleshooting
Safety first: Turn off power before working on thermostat or control wiring.
- 1. Verify thermostat operation: Turn the thermostat to OFF or well below room temperature. If the boiler continues to run, the issue is likely in wiring or the control.
- 2. Inspect thermostat wiring: At the boiler or zone panel, look for thermostat wires that are shorted together or pinched.
- 3. Check control relays (visual): Some controls have visible relays. If a relay appears burned or stuck, the control may need replacement.
- 4. Temporarily disconnect call for heat: With power off, disconnect the thermostat or TT terminals. Restore power. If the boiler still runs, the control is likely faulty and requires replacement.
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Repair Difficulty
Hard
4/5
Required Part
Integrated Boiler Control Module
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