Safety Warning
Code 13 indicates dangerous overheating. Turn off your furnace and investigate immediately. Do not ignore this error.
What Does Code 13 Mean?
Limit Switch Has Opened
Safety shutdown due to excessive temperature
Carrier Code 13 (13 LED flashes) indicates that the limit switch has opened because your furnace reached an unsafe temperature. The limit switch is a critical safety device that prevents fire hazards by shutting down the burner when temperatures exceed safe limits.
Common Causes
Dirty Air Filter
Most common cause - restricts airflow
Blocked Vents
Closed registers or furniture blocking airflow
Blower Motor Issues
Not moving sufficient air
DIY Troubleshooting Steps
Safety First
Turn off power at the breaker before checking your furnace.
Step 1: Replace Air Filter
Check and replace if dirty or clogged
Step 2: Check All Vents
Open all registers and remove obstructions
Step 3: Reset the System
After fixes, power cycle and test