13
Limit circuit lockout
This code typically points to
- Limit or rollout switch open more than 3 minutes
- 10 successive limit trips during high heat
- Dirty filter, weak blower, wrong airflow setup
- Venting/combustion issue if rollout is involved
Next checks to confirm
- Determine whether the open device is main limit or rollout
- Verify airflow/static/blower operation
- Inspect venting/burner/heat-exchanger area if rollout is implicated
Escalation
Manual-reset rollout or recurring limit trip after airflow corrections indicates a harder safety/combustion problem.
Reset behavior
Auto-resets after 3 hours.
Safety Critical
Immediate concern