Status LED shows 3 flashes, inducer may start but burners do not light, furnace shuts down.

Safety: Turn off power and gas before servicing. Do not operate the furnace with venting disconnected.

Steps to check:

• Check vent pipes: Inspect PVC intake and exhaust pipes from furnace to outside. Look for sags holding water, separations, or obstructions at terminations. Clear debris and correct any low spots that collect condensate.
• Clean condensate trap and drain: On Ruud high-efficiency models, locate the condensate trap assembly. Remove hoses, flush the trap with warm water until clear, and ensure the drain line to the pump or floor drain is not blocked or kinked.
• Inspect pressure switch tubing and ports: Remove the tubing from the inducer and pressure switch. Use a small drill bit or paper clip (by hand only) to gently clear any debris from the inducer port. Reattach tubing securely.
• Test inducer motor: With power restored, observe if the inducer starts promptly and runs smoothly. If it hums, is noisy, or fails to start, the inducer assembly may need replacement.
• Verify condensate pump (if used): If a condensate pump is installed, ensure it is powered and pumping. A failed pump can cause water backup and pressure switch faults.