Furnace LED displays code 33; unit may run briefly then shut down; blower may continue to run.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety: A rollout condition can be hazardous. If you see scorch marks or smell strong combustion fumes, shut off the furnace and call a professional.
Steps to check (airflow-related):
- Filter and vents: Replace dirty filters and ensure all vents are open.
- Blower operation: Confirm the blower starts on time and runs at the correct speed. Weak airflow suggests motor or capacitor issues.
- Reset rollout (if tripped and safe): After cooling, press the reset button on any manual-reset rollout switches near the burners. If they trip again, stop and call a technician.
When to call a pro: A technician should inspect the heat exchanger, flue, and burner alignment, and test/replace limit and rollout switches as needed.
Repair Difficulty
Required Part
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