HVAC Code Lookup

Carrier Furnace Code 13

Soft lockoutShown as: 1 short flash, 3 long flashes

Limit circuit lockout. The limit switch, draft safeguard, flame rollout, or blocked-vent switch has stayed open longer than 3 minutes (or the furnace tripped the limit 10 times in a row on high heat). The control locks out and auto-resets after 3 hours.

Manual wording: “13 LIMIT CIRCUIT LOCKOUT - Lockout occurs if the limit, or flame rollout switch is open longer than 3 minutes or 10 successive limit trips occurred during high-heat. Control will auto reset after 3 hours.”

Documented for: 58SC0A, 58SC0B, 58MCB, 58MVP, 58UVB

Likely causes, most common first

  1. The furnace repeatedly overheated - almost always an airflow problem (see code 33 for the full cause list)
  2. Flame rollout switch tripped, which requires manual reset by a technician
  3. Defective limit switch or connections

What you can safely check yourself

  • Check the air filter and replace it if it is dirty - restricted airflow is the number one cause
  • Make sure supply registers and return grilles are open and not blocked by furniture or rugs
  • Check that the furnace door is fully closed

When to call a technician

Code 13 means the furnace has been overheating. Even if a new filter clears it, have a technician verify why the limit was tripping - a flame rollout trip in particular is a combustion problem that must be diagnosed before the furnace is put back in service.

A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Carrier codes