Error code 18 and furnace shuts down with water present in cabinet or around base

Safety: Turn off power before working around water and electrical components.

Error 18 indicates a condensate drainage problem.

• Inspect and clean trap:
  • Remove the plastic condensate trap.
  • Flush with water and a small brush to remove slime and debris.
• Clear drain line:
  • Use a wet/dry vacuum at the drain termination to pull out clogs.
  • Ensure the line slopes continuously downward with no sags.
• Check for pan cracks:
  • Look for leaks around the secondary heat exchanger drain connections.
  • Replace cracked pans or fittings with OEM parts.
• After cleaning, pour water into the trap to prime it before restarting the furnace.