Error code 09 and furnace attempts to start but shuts down with blower running for cool-down

Safety: Turn off power before accessing the blower compartment or coil.

Error 09 points to an open auxiliary or secondary limit switch.

• Inspect the evaporator coil (if present):
  • Remove the coil access panel above the furnace.
  • Check for heavy dust, pet hair, or ice buildup restricting airflow.
  • Have the coil professionally cleaned if dirty.
• Check duct restrictions:
  • Open all zone dampers and registers.
  • Look for crushed or disconnected flex duct.
• Test auxiliary limit switches:
  • Locate limits on the blower housing or near the coil.
  • With power off, test for continuity when cool. Replace any open switches with OEM-rated American Standard parts.
• If overheating persists, have a technician evaluate furnace sizing and blower speed settings.