Pressure Switch Stuck Closed
Weil-McLain
Combustion Pressure Switch Not Opening at Rest
Control indicates 'Pressure Switch Closed' when idle; unit will not start a new cycle.
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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
Shorted pressure switch contacts, Pressure tubing misrouted or pinched, Inducer housing blocked, Control board sensing fault
How to Fix / Troubleshooting
Safety first: Turn off power and gas before servicing.
- Inspect tubing and ports: Remove pressure tubing from the switch and inducer. Ensure ports are clear and not plugged with debris or condensate. Correct any kinks or misrouting.
- Check switch at rest: With tubing removed and power off, gently tap the pressure switch body. If it remains electrically closed (requires meter to confirm), the switch is likely stuck and should be replaced.
- Verify inducer is not running continuously: A stuck relay on the control board could keep the inducer on, affecting pressure readings. If the inducer runs with no call for heat, the control module may be faulty.
- Replace switch if defective: Install a new Weil-McLain specified pressure switch, matching the rating and port configuration.
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Repair Difficulty
Medium
3/5
Required Part
Combustion Air Pressure Switch
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