Furnace LED shows code 23 (pressure switch did not open), inducer may run continuously even with no call for heat.

Safety first: Turn off power before disconnecting any tubing or wires.

• Inspect pressure switch tubing: Locate the rubber or silicone tube from the inducer housing to the pressure switch. Remove it and check for water, debris, or kinks. Blow gently through the tube to clear any blockage and reinstall securely.
• Check vent and intake: For Carrier condensing furnaces with PVC venting, go outside and inspect the exhaust and intake pipes for ice, leaves, nests, or other obstructions. Clear any blockage.
• Test switch operation (basic): With power off, disconnect one wire from the pressure switch and check if the code changes when power is restored. If the board still reads the switch as closed, the control may be faulty.
• Look for water in inducer housing: On high-efficiency models, ensure the condensate drain from the inducer and collector box is not clogged, which can hold the pressure switch closed.

If the pressure switch remains stuck closed or the code persists, the pressure switch or control board should be tested and replaced by a professional.