York
High Limit Trip During Warm-Up
Furnace burners light but shut off after 30–90 seconds; blower may or may not start.
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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.
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Possible Causes
Severely restricted airflow, Oversized furnace, Blower motor not starting on time, Dirty evaporator coil above furnace
How to Fix / Troubleshooting
Safety: Turn off power before opening blower or coil compartments.
- Filter and registers: Replace dirty filters and open all registers. This alone often resolves limit trips.
- Check blower operation: Observe if the blower starts within 30–60 seconds of burner ignition. If delayed or not starting, the blower motor or control timing may be faulty.
- Inspect evaporator coil: If you have central AC, the A-coil above the furnace can be clogged with dust. Remove the access panel (if present) and visually inspect. Cleaning a heavily impacted coil is best done by a technician.
- Monitor operation: After cleaning and filter replacement, run the furnace and watch for normal continuous operation. If it still cycles off on limit, call a professional to check static pressure and sizing.
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Repair Difficulty
Medium
3/5
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