Carrier 58MVC Error Code Status Code 13: Limit Circuit Lockout

What Does Code Status Code 13 Mean?

Code 13 is a safety lockout that triggers when the furnace's high-temperature limit switch or flame rollout switch has been open for more than 3 minutes, or when 10 successive limit switch trips have occurred during high-heat operation. The limit switch is a safety device that shuts off the gas burners when the heat exchanger gets too hot, preventing damage and fire risk.

The most common reason the heat exchanger overheats is restricted airflow. When the air filter is clogged or supply/return vents are blocked, the blower cannot move enough air across the heat exchanger to carry heat away. The exchanger temperature rises, the limit switch opens, and the burners shut off. If this cycle repeats enough times, the control locks out with code 13.

The furnace will automatically reset after 3 hours. However, if you don't fix the underlying airflow problem, the lockout will simply happen again. Code 13 is related to code 33 — a single limit switch trip shows as code 33, and repeated trips escalate to the code 13 lockout.

Limit or flame rollout switch open during operation triggers code 33 first, repeated occurrences escalate to lockout code 13. The system will escalate to error code 33 .

Common Causes

How to Fix It: Check Air Filter and Airflow

What You'll Need

• Replacement air filter (if needed)
• Flashlight

Steps

1. Turn off power at the breaker or power switch AND shut off the gas supply Locate the furnace circuit breaker and turn it OFF. Find the gas shutoff valve on the supply line to the furnace and turn it to the closed position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
2. Check and replace the air filter Locate the air filter — on the 58MVC it is typically found at the bottom of the furnace or in the return air duct. Slide the filter out and inspect it. If you can't see light through it or it is visibly clogged with dust and debris, replace it with a new filter of the same size. A dirty filter is the most common cause of limit circuit lockouts.
3. Check all supply and return vents throughout the house Walk through every room and make sure all supply registers and return air grilles are fully open and unobstructed. Move furniture, rugs, or curtains that may be blocking airflow. Even one or two blocked returns can cause enough airflow restriction to trigger overheating.
4. Restore power and gas, then wait for the auto-reset Turn the gas supply valve back to the open position (parallel to the pipe). Turn the breaker back ON. The control will auto-reset after 3 hours from when the lockout occurred. If you just fixed the filter and vents, the furnace should operate normally after the reset period.

When to Call a Professional

Contact a licensed HVAC technician if:

• Code 13 returns after replacing the filter and confirming all vents are open
• The flame rollout switch has tripped (this is a red button on the switch that must be manually reset — do not reset it yourself without professional inspection)
• You notice unusual noises from the blower or the blower does not seem to be running at full speed
• The furnace smells like it is overheating or you see discoloration on the heat exchanger area
• The lockout occurs frequently (more than once per heating season)