Bryant Furnace Error Code 33 – Meaning, Causes & Fix

What Does 33 Mean?

What Causes This Error?

• Severely clogged air filter restricting airflow over the heat exchanger
• Supply or return vents closed, blocked, or covered
• Blower motor failed or not running at full design speed
• Blower run capacitor failed, causing sluggish motor performance
• Rollout switch tripped due to flame rollout event
• Cracked heat exchanger allowing combustion gas to affect temperature sensors
• Blocked flue exhaust restricting combustion heat removal
• Auxiliary limit switch fatigued or miscalibrated, tripping prematurely

How to Fix 33

1. 1

   Confirm error code 33. Look through the diagnostic window on the Bryant furnace access panel. Count the blink pattern: 3 blinks, pause, 3 blinks, repeat. Confirm against the fault code chart on the inside of the access panel door — on Bryant furnaces, 3-3 should correspond to 'Limit Circuit Open.' Different Bryant models may have slight variations in fault code assignments.

2. 2

   Replace the air filter. This is the first and most impactful step. Locate and remove the air filter. If it is gray, brown, or visibly clogged, it is the likely cause. Replace with a new filter of the correct size (MERV 8 or below for most Bryant residential furnaces). After replacing the filter, allow the furnace to cool for 30 minutes, then attempt a heat call. Many code 33 errors on Bryant furnaces are permanently resolved by a filter change alone.

3. 3

   Check all vents and registers. Walk through the entire home and ensure every supply register (air out) and return grille (air in) is fully open and unobstructed by furniture, rugs, or stored items. On Bryant two-stage and variable-speed systems, even partial vent blockage can cause high limit trips during extended high-fire operation.

4. 4

   Verify blower motor operation. Set the thermostat to Fan Only mode to test the blower independently. Listen and feel supply registers for strong, consistent airflow. If airflow is weak, the blower motor or run capacitor may be failing. A motor that hums without building speed, or does not start, has a failed run capacitor or motor winding fault. Do not continue running the furnace with a failing blower.

5. 5

   Inspect for a tripped rollout switch. Open the furnace burner compartment access panel. Locate the rollout switch(es) — small disc-shaped components with a button on top, mounted near the burner manifold. If the button is popped out (not flush), the rollout switch has tripped and must be manually reset by pressing the button. However, a tripped rollout switch indicates a genuine flame rollout event — caused by a blocked flue, cracked heat exchanger, or combustion air issue — and must be investigated by a technician before resuming operation.

6. 6

   Inspect the flue pipe. Go outside and visually inspect the furnace flue exhaust pipe. On PVC-flued 90%+ models, check both the exhaust and intake pipes for blockages — birds nests, ice, or debris. On metal-flued 80% models, inspect the visible flue sections for disconnected joints, visible damage, or blockage. A blocked flue causes combustion heat to back up into the furnace, overheating the heat exchanger and tripping the limit circuit.

When to Call a Professional

Can You Still Use the Device?

Do not continue to operate the Bryant furnace while code 33 is active or recurs repeatedly. The limit circuit is protecting the heat exchanger from catastrophic damage. Repeated overtemperature cycles accelerate heat exchanger fatigue and can cause cracking, creating a carbon monoxide risk. Resolve the airflow or mechanical fault completely before resuming heating.