13HIGH
Limit Circuit Lockout (Lennox)
Lennox furnace has detected the limit switch opened 5 times in a single call for heat, locking out the system.
What This Error Code Means
The limit circuit has opened repeatedly, indicating a persistent overheating condition that requires investigation.
Common Causes
- Severely restricted airflow
- Blower motor failure
- Dirty evaporator coil
- Return duct undersized
- Failed limit switch
Affected Brands
Lennox
How ROMA Heating Fixes This
- Replace air filter and check static pressure
- Test blower motor capacitor and amp draw
- Inspect evaporator coil for dirt
- Verify duct sizing and return air
- Replace limit switch if defective
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