Bryant 355MAV Error Code 33: Limit Circuit Fault

What Does Code 33 Mean?

Status code 33 on the Bryant 355MAV means the limit switch or flame rollout switch is currently open. This is an active fault — the furnace detected overheating and the safety switch tripped. The blower will run for 4 minutes or until the open switch remakes (closes again), whichever is longer. If the switch stays open for more than 3 minutes, the code will escalate to lockout code 13.

The most common cause is restricted airflow from a dirty or clogged air filter. When the filter is blocked, heat builds up in the heat exchanger because the blower cannot move enough air across it. The limit switch senses the excessive temperature and opens to protect the furnace and heat exchanger from damage.

The 355MAV can also enter code 33 if it is operating in high-heat only mode due to 2 successive low-heat limit trips. This happens when the low-heat gas input is too high for the available airflow. If the flame rollout switch has tripped (rather than the limit switch), this is a more serious condition requiring professional diagnosis — the rollout switch requires manual reset.

If limit or flame rollout switch is open longer than 3 minutes. The system will escalate to error code 13 .

Common Causes

How to Fix It: Check Air Filter and Vents

What You'll Need

• Replacement air filter (same size as current filter)
• Flashlight

Steps

1. Turn off power at the breaker or power switch and shut off the gas supply valve Locate your electrical panel and turn the furnace breaker to OFF. Find the gas shutoff valve on the gas line leading to the furnace and turn it to the closed (perpendicular to the pipe) position. If you smell gas, leave immediately and call your gas company.
2. Locate and inspect the air filter The air filter is typically located in the blower compartment or the return air duct near the furnace. Slide it out and hold it up to a light. If you cannot see light through it, or if it is heavily coated with dust and debris, it needs to be replaced immediately.
3. Replace the air filter if dirty Insert a new filter of the same size. Make sure the airflow direction arrow on the filter frame points toward the furnace (toward the blower). A clogged filter is by far the most common cause of limit circuit faults on this model.
4. Check all return air vents and supply registers Walk through your home and confirm all return air grilles and supply registers are open and unblocked. Move any furniture, rugs, curtains, or other items that may be restricting airflow. Closing too many registers in unused rooms can also cause overheating.
5. Restore power and gas Turn the gas supply valve back to open (parallel to the pipe). Turn the breaker back ON. The furnace should resume normal operation once the limit switch cools down and closes.

When to Call a Professional

Contact a licensed HVAC technician if:

• Code 33 returns after replacing the air filter and opening all vents
• The flame rollout switch has tripped (it has a manual reset button — do not repeatedly reset it)
• You hear unusual noises from the blower suggesting a loose blower wheel
• The furnace trips the limit only during high-heat operation
• Code 33 consistently escalates to lockout code 13 despite a clean filter
• The blower runs but produces noticeably weak airflow