The sequence, from Carrier's manual: a limit or flame roll-out switch opens and the board shows 33. Three minutes later, still open, the board changes the code to 13 and locks the furnace out. The control will auto-reset after three hours — but "auto-reset" deserves a hard look. If the open switch is the roll-out, the switch itself is manual-reset hardware; the board can forgive the lockout and the furnace still will not run until someone resets that switch and answers for why it opened.
If the open switch is the main limit, the three-hour wait usually ends with the furnace trying again — and tripping again, if the airflow problem is still there. A 13 that follows a filter change and open registers is a blower or switch diagnosis now.
Code 13: Limit or flame roll-out switch lockout
Safety stop — furnace off, call a technician
The lockout version of code 33. The control auto-resets after three hours; the flame roll-out switch itself needs a manual reset. Read code 33 for the cause list.
From the table: Two-digit status codes — short flashes, then long flashes — source: Carrier 58YAV Service section - status code table (read the document, fetched 2026-10-30). Covers: Carrier 58-series and their Bryant/Payne twins. First digit = number of short flashes; second digit = number of long flashes. Code 33 is 3 short, pause, 3 long.
What not to do with a 13
Do not spend the three hours cycling power to hurry it. The lockout is the control's way of making a repeated overheat or roll-out event impossible to ignore, and every manual reset of a roll-out switch without a cause is a small gamble. Photograph the code, do the airflow basics, and let the technician arrive to a furnace that still remembers what happened.
Safety stop — furnace off, call a technician — the safe list:
- Turn the furnace off at its power switch and leave it off.
- This code means the control thinks flame or gas is present when it should not be, or that a flame-safety switch has opened. Resetting it is not a fix.
- Call a licensed HVAC technician. If you smell gas at any point: leave the house and call your gas utility or 911 from outside.
The two rules that outrank everything on this page.
1. Smell gas? Stop reading. Leave the house and call your gas utility or 911 from outside. No code is worth diagnosing through a gas smell.
2. Never bypass a safety switch — no jumping a pressure switch, no taping a limit, no propping a rollout. Those switches are the only thing between a furnace fault and a fire or carbon-monoxide problem. This library explains codes; it does not teach repairs inside the cabinet.
One honesty note before the tables: codes change between control boards, sometimes inside the same brand and the same decade. Every table below names the board and the manual it was transcribed from. The chart glued inside your own blower door is the final word for your furnace — if it disagrees with this page, believe the door.