What the Error Code Means
Error code 13 generally means the furnace detected a safety condition related to heat or airflow and shut down.
It indicates a protective response rather than a single confirmed failure.
Common Symptoms You May Notice
- The furnace starts but shuts off before delivering steady heat.
- The blower may continue running while heat stops.
- You see the 13 code flashing on the control panel or indicator light.
Most Common Causes (From Least to Most Serious)
- Restricted airflow: A dirty filter, blocked vents, or closed registers can reduce airflow and trigger a safety stop.
- Return air is limited: Obstructions around return grilles can make it harder for air to circulate properly.
- System is running hotter than expected: In many cases the furnace pauses when it senses heat conditions outside the normal range.
Safe Things You Can Check Yourself
- Turn the thermostat off, wait a minute, and set it back to heat to see if the code clears.
- Replace or clean the furnace filter if it looks dusty or clogged.
- Make sure supply vents and return grilles are open and not blocked.
If at any point this feels unsafe or unclear, stop and contact a professional.
When to Stop and Call for Service
- The code returns quickly after a reset or during every heating cycle.
- You smell burning, see smoke, or the system shuts down repeatedly.
- The furnace will not produce heat even after basic airflow checks.
Typical Repair Cost Range
$150-$450 is typical for diagnosis and service to address furnace safety shutdowns, depending on the cause and parts involved.
Costs vary by region, model, and provider. Request an estimate before approving any repair.