System Diagnosis
Limit Circuit Lockout. Lockout occurs if the limit or flame rollout switch is open longer than 3 minutes or after 10 successive limit trips during high heat; auto reset after 3 hours.
Carrier | Furnaces
Error Code 13
Troubleshooting guide for the Carrier Furnaces system fault 13.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
Potential Causes & Solutions
- Check for restricted airflow (dirty filter, blocked registers).
- Inspect limit switch and flame rollout switch for continuity.
- Verify blower motor operation.
- Check heat exchanger for cracks or obstructions.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and furnaces context before acting on a generic code description.
- Walk the entire heating sequence in order instead of jumping straight to the reported code.
- Verify each safety device and prove where the sequence stops under live operation.
- After the correction, run the system long enough to confirm the code does not return under normal load.
Field Signals to Confirm
What usually confirms it
A repeatable stop in the heating sequence at the same safety or prove step.
What can fool you
Weak grounding, marginal flame signal, or venting issues can produce inconsistent code behavior.
When to Escalate the Call
- Safety devices keep opening after the obvious mechanical causes are corrected.
- Combustion, venting, or gas input needs a higher-confidence review.
Diagnose with Confidence
Use the ACLogics AI assistant to walk through this error code step-by-step.
Included in Diagnosis Workflow
Ask
Upload nameplate & symptoms
Diagnose
AI isolates the likely furnaces branch behind code 13
Report
Document the verified result and next action