Furnace starts inducer but does not light; LED flashes 3 times repeatedly; you may hear clicking from the ignitor but no flame.

Safety: Shut off power and gas before working on venting. Use caution on ladders or roofs.

Steps:

• Inspect the PVC vent and intake (if 2-pipe) from the furnace to the termination. Remove any visible obstructions such as leaves, nests, or ice. Ensure terminations meet Tappan clearance requirements.
• Check the rubber pressure switch tubing for splits, loose connections, or water accumulation. Replace damaged tubing and ensure a snug fit on the inducer and switch ports.
• Restore power and call for heat. Listen for the inducer. If it hums but does not spin or is very weak, the inducer motor assembly may be failing and not generating enough draft to close the pressure switch.
• With the inducer running, measure continuity across the pressure switch. It should close (show continuity). If it remains open with proper venting and a strong inducer, replace the pressure switch.

Warning: Do not modify or shorten vent lengths beyond what is specified on the Tappan installation label; improper venting can cause carbon monoxide hazards.