Pressure Switch Closed
Weil-McLain
Stuck or Shorted Air Pressure Switch
Control indicates 'Pressure Switch Closed' or 'Stuck Closed' when there is no call for heat; boiler may not start.
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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
Pressure switch contacts welded closed, tubing misrouted to constant pressure source, defective control board input
How to Fix / Troubleshooting
Safety first: Power off the boiler before testing the switch.
- 1. Inspect tubing routing: Verify the pressure tubing is connected exactly as shown in the Weil-McLain installation manual. Incorrect connections can hold the switch closed.
- 2. Check for water in tubing: Remove the tubing from the switch and inducer. Drain any condensate and reinstall with proper slope to prevent water traps.
- 3. Test switch mechanically: With power off, gently press on the switch diaphragm area (if accessible) and listen for a click. If it feels stuck or does not click, replacement is recommended.
- 4. Reset control: Restore power and reset the boiler. If the fault returns immediately, the switch or control input may be defective.
Replacement of the pressure switch or control board should be done by a qualified technician.
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Repair Difficulty
Medium
3/5
Required Part
Air Pressure Switch
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