Pressure Switch Open
Weil-McLain Combustion Air Proving Failure

Boiler will not ignite; control shows 'Pressure Switch Open', 'Air Proving Switch Open', or similar; inducer may run continuously.

Advertisements

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.

Advertisements

Possible Causes

Blocked vent or intake, failed air pressure switch, cracked or disconnected pressure tubing, inducer fan not running at speed

How to Fix / Troubleshooting

Safety first: Turn off power before disconnecting any tubing or wiring. Do not bypass safety switches.

  • 1. Inspect vent and intake: Check the PVC vent and combustion air intake for obstructions, sagging, or water accumulation. Clear blockages and correct pipe slope.
  • 2. Check pressure tubing: Locate the rubber or silicone tubing from the inducer to the air pressure switch. Ensure it is firmly connected, not cracked, kinked, or filled with water. Replace if damaged.
  • 3. Verify inducer operation: On a call for heat, confirm the inducer motor starts and runs smoothly. Listen for unusual noises or slow startup.
  • 4. Gently tap pressure switch: With the inducer running, lightly tap the pressure switch body. If the boiler suddenly fires, the switch may be sticking and should be replaced.

If the error persists after clearing venting and tubing, a technician should test the pressure switch and inducer with proper instruments.

Advertisements

Repair Difficulty

Medium 3/5

Required Part

Air Pressure Switch
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements