Furnace displays F05 and shuts down; may occur during blower ramp-up.

Safety: Turn off power. Condensate water may be dirty; have towels or a container ready.

Steps:

• Locate the condensate trap and drain tubing on your high-efficiency Westinghouse furnace.
• Disconnect the tubing and inspect for slime, debris, or kinks. Flush the tubing with warm water and a small amount of mild bleach solution, then rinse thoroughly.
• Remove and clean the condensate trap if accessible; ensure all passages are clear.
• Verify that the drain line slopes continuously downward to the floor drain or pump.
• Check the pressure switch tubing for water; drain and reattach securely.
• Restore power and test operation. If F05 returns, a technician should check for internal heat exchanger or collector box blockage.