Furnace will not start; LED shows 6 flashes; inducer may run briefly then stop.

Safety: Turn off power and gas before servicing venting or condensate components.

Steps:

• Inspect condensate system: For condensing Goodman furnaces, remove and clean the condensate trap. Flush with warm water to remove sludge. Ensure drain lines are clear and properly sloped to the drain.
• Check vent pitch and joints: Verify PVC vent pipes slope back toward the furnace (for condensate return) and that all joints are glued and sealed. Look for sags where water can collect.
• Monitor pressure switch during run: With a multimeter, check continuity across the pressure switch while the furnace is running. If it opens intermittently, the switch may be weak or the inducer/venting is marginal.
• Shorten or correct venting if possible: Compare vent length and number of elbows to the Goodman installation manual. Excessive length or elbows can cause draft issues and may require re-piping by a professional.

If the 6-flash code persists after cleaning condensate and verifying venting, have a technician measure draft and replace the pressure switch or inducer as needed.