E3
Primary limit or auxiliary limit circuit is open; rollout limit circuit is open
This code typically points to
- Insufficient conditioned airflow
- Blocked filters
- Restrictive or improper ductwork
- Blower speed too low
- Failed blower motor
- Flame rollout
- Misaligned burners
- Blocked flue/air inlet
- Failed induced-draft blower
- Loose/improper wiring
Next checks to confirm
- Check filters/ductwork
- Check circulator blower speed/performance
- Check burners for proper alignment
- Check flue and inlet piping
- Check induced-draft blower
- Tighten/correct wiring
Escalation
Circulator blower runs continuously; no furnace operation until limit condition clears
Reset behavior
Clears after the open limit/rollout circuit returns to normal and underlying cause is corrected.
Safety Critical
Immediate concern