Bryant 315AAV Error Code 33: Limit Circuit Fault

What Does Code 33 Mean?

Status code 33 on the Bryant 315AAV indicates a limit circuit fault. A safety switch — such as the high-temperature limit, draft safeguard, flame rollout, or blocked vent switch — has opened because the furnace detected an unsafe condition. The blower will run for at least 4 minutes or until the open switch recloses, whichever is longer. If the switch stays open for more than 3 minutes, the code will escalate to status code 13 (limit circuit lockout).

Additionally, if 2 successive low-heat limit trips occur, the furnace will switch to high-heat only mode as a protective measure. This means you may notice the furnace running louder than usual or producing more heat than expected.

The most common cause is a dirty air filter or restricted duct system that limits airflow across the heat exchanger. When air cannot flow freely, heat builds up inside the furnace and the limit switch opens to prevent damage. Other causes include restricted venting, excessive wind, improper vent sizing, or inadequate combustion air supply. A defective limit switch itself is less common but possible.

Common Causes

How to Fix It: Replace the Air Filter and Check Airflow

What You'll Need

• Replacement air filter (correct size for your system) 🛒 Find at FiltersFast · 🛒 Find at Amazon
• Flashlight

Steps

1. Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
2. Check and replace the air filter Remove the air filter from the return air duct or furnace filter slot. If it is visibly dirty, clogged, or has not been changed in over 3 months, replace it with a new filter of the correct size. Make sure the airflow direction arrow on the new filter points toward the furnace.
3. Verify all supply and return vents are open Walk through every room and ensure all supply registers and return grilles are fully open and not blocked by furniture, curtains, or rugs. Restricted airflow from closed vents is a common contributor to overheating.
4. Check the exhaust vent for restrictions Inspect the exhaust vent from the furnace to the outdoor termination. Look for blockages at the outdoor opening (ice, snow, debris) and any sagging sections in horizontal pipe runs. Clear any obstructions you find.
5. Verify combustion air supply is adequate If your furnace draws combustion air from the surrounding space, make sure the area around the furnace is not too confined or sealed off. Check that combustion air intake pipes (if installed) are clear and unblocked.
6. Restore power and gas, then test Turn the gas supply valve to ON and flip the circuit breaker to ON. Set your thermostat to call for heat and monitor the furnace through a complete heating cycle. Watch through the sight glass on the blower access door to check for the LED status.

When to Call a Professional

Contact a licensed HVAC technician if:

• Code 33 returns after replacing the filter and opening all vents
• The code escalates to code 13 (limit circuit lockout) despite your efforts
• The flame rollout switch has tripped (a red button on the switch needs manual reset)
• The furnace stays stuck in high-heat only mode
• You suspect the vent system may be improperly sized for this furnace

✓ Verified against manufacturer service manual — March 2026