What It Means
Limit switch or flame rollout switch remained open longer than 3 minutes, causing a system lockout.
Bryant Furnace
Bryant Furnace Error Code 13
Troubleshooting guide for the Bryant Furnace system fault 13.
Possible Causes
- Restricted airflow from dirty filter, blocked registers, or undersized ductwork.
- Faulty or open limit or flame rollout switch.
- Failing or miswired blower motor reducing airflow.
- Cracked, blocked, or soot-covered heat exchanger trapping heat.
Not sure which one it is — or if it's none of these? Try ACLogics today.
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.
New to this code? Click to see why this happens
Full Diagnosis
Limit Circuit Lockout. The control shuts down the gas valve and locks out the burner when the limit switch or flame rollout switch stays open for longer than 3 minutes straight, cutting heat production while leaving the blower running to dissipate residual heat in the heat exchanger. This is the lockout counterpart to code 33 (limit circuit fault) — 33 is the live, self-clearing indication that a limit or rollout switch is currently open, and it escalates into lockout 13 only if that open condition persists past the 3-minute threshold. The control auto-resets after 3 hours, the same interval used for ignition lockout (code 14), but the underlying trigger is different: 13 is driven by an overheat/rollout condition, while 14 is driven by repeated failed ignition attempts. If 13 recurs immediately after reset, suspect airflow or heat exchanger restriction rather than an ignition problem.
All Recorded Causes
Check for restricted airflow (dirty filter, blocked or closed supply/return registers, undersized ductwork) — the most common cause of nuisance limit trips. Inspect the limit switch and flame rollout switch for continuity and confirm neither is mechanically stuck open. Verify blower motor operation and airflow match the furnace's rating; a failing or miswired blower lets the heat exchanger overheat under normal gas input. Check the heat exchanger for cracks, blockage, or soot buildup that traps heat near the limit switch. Auto-resets after 3 hours; if the lockout repeats on the next call for heat, the airflow or switch problem has not been resolved.
Verify Before Replacing Parts
- Confirm the exact Bryant 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, watching for check for restricted airflow (dirty filter, blocked or closed supply/return registers, und….
- Verify each safety device and prove where the sequence stops under live operation, including whether inspect the limit switch and flame rollout switch for continuity and confirm neither is me….
- After the correction, run the system long enough to confirm the furnaces fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Bryant Furnace diagnostics step-by-step — so you confirm the cause before swapping parts.
