4 Flashes
Limit switch open; downflow note calls out auxiliary limit open on downflow-only applications
This code typically points to
- Open main or auxiliary limit
- Airflow restriction, blower issue, dirty filter, or overfire
Next checks to confirm
- Check limit continuity and application-specific auxiliary limits
- If remade, confirm airflow and temperature rise
Escalation
If limit repeats, move to airflow / blower / input check.
Reset behavior
Clears when limit remakes and heat cycle is reattempted.
Urgent
Fix now