Furnace starts inducer but burners do not light; status LED shows 3 red flashes repeating; you may hear the ignitor but no flame.

Safety first: Shut off power before removing panels. Do not operate the furnace with venting disconnected.

Steps to check:

• Inspect outdoor vent terminations: For direct-vent Coleman furnaces, check both intake and exhaust PVC terminations for obstructions (ice, snow, leaves, bird nests). Clear any blockage and ensure proper clearances from snow and vegetation.
• Check pressure tubing and ports: Remove the rubber tube from the pressure switch and the inducer port. Use a small drill bit or paper clip (by hand only) to gently clear any debris from the inducer port. Reattach tubing securely and ensure there are no kinks or sags holding water.
• Verify inducer operation: Restore power and call for heat. Confirm the inducer starts promptly and runs smoothly. If it is slow to start, noisy, or stops intermittently, the inducer assembly may be weak and not generating enough draft to close the pressure switch.
• Test pressure switch closing: With a multimeter, check for continuity across the pressure switch terminals after the inducer starts. If it never closes (remains open) despite good venting and inducer operation, replace the pressure switch with a Coleman-specified part.

If venting or combustion air issues are suspected, have a licensed technician verify draft, combustion, and vent sizing.