Normal Operation
System is powered and in standby with no stored faults.
Diagnostic Steps
- No action needed
System Lockout
Furnace locked out after maximum retries.
Probable Causes
- Ignition failure
- Flame proving failure
Diagnostic Steps
- Power cycle to reset
- Clean flame sensor
- Test igniter
- Check gas supply
Pressure Switch Error
Pressure switch stuck open or failed to close.
Probable Causes
- Blocked vent
- Bad pressure switch
- Inducer failure
Diagnostic Steps
- Check flue pipes
- Test pressure switch
- Inspect inducer motor
Open Limit Circuit
High limit or rollout switch has opened.
Probable Causes
- Dirty filter
- Low airflow
- Rollout trip
Diagnostic Steps
- Replace filter
- Check airflow
- Inspect rollout switches