The short answer
Code 33 on a Bryant furnace in Northern Virginia means a switch in the limit circuit opened: the main limit, which trips when the furnace runs too hot, or a rollout switch, which trips when flame shows up where it shouldn’t. Most 33s are airflow. A clogged filter, closed registers or a dirty blower wheel let the heat build up until the limit opens. A rollout trip is a different story and a call for us.
What you’ll notice
- The furnace heats for a few minutes, the burners shut off, and the blower keeps running.
- It cycles like that over and over, and the house never quite warms up.
- The light flashes 3 short, then 3 long, or the display shows 33.1.
- After a while it flashes 13 instead and stops trying.
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How to read the code
Bryant furnaces have one of two kinds of control board. One has only an amber light behind the small window in the lower door: short flashes are the first digit and long flashes are the second, so 33 is 3 short and 3 long, then a pause before it repeats. The other has the same light plus a small display that shows three digits, like 33.1: the first two are the flash code and the third narrows it down. A steady light is normal, no light at all means no power at the board, and rapid flashing means the line voltage polarity is reversed. Both boards in Bryant’s current manuals keep the code through a power cut, but some older furnaces erase it, so count it before you flip the switch.
What Bryant’s board does on a 33
When the limit opens, the board shuts off the gas and runs the blower to cool the furnace down, for 4 minutes or until the switch closes again. If the switch stays open more than 3 minutes, the code becomes 13, a limit lockout, and the board waits 3 hours before it tries again. So a furnace flashing 13 has been through a string of 33s.
What causes code 33
These are the checks in Bryant’s 915SB manual for a 33, with the ones you can look at first.
Swipe to see all columns →
Swipe to see all columns →
| Cause | What it looks like | Can you check it? |
|---|---|---|
| Dirty filter or restricted ducts | A gray filter you can’t see light through; registers closed or blocked by furniture | Yes |
| Loose or dirty blower wheel | Weak airflow at every register, a rattle at start-up | No: we clean or tighten it |
| Blower motor | The blower is slow, hums, or doesn’t run at all | No: we test the motor and capacitor |
| Restricted vent or wrong vent size | Mostly after a remodel or a new install | Look at the pipe ends outside |
| Not enough combustion air | A furnace closet that got closed in | Partly: open the closet |
| The switch or its wiring | 33 with good airflow and a clean filter | No: we test it |
What you can safely check
- Pull the filter. If it’s clogged, change it, and our filter guide covers which one to buy. A thick, high-MERV filter on a furnace that wasn’t set up for one can choke the airflow by itself.
- Open every supply register and clear the return grilles. Closing off rooms to save money raises the furnace’s temperature.
- If the furnace is in a closet, leave the door open and see if it runs longer.
- Turn the furnace switch off for 30 seconds, back on, and let it try once.
When it’s the rollout switch
Rollout switches are small round disks with a button, on the burner box. Bryant’s manual says the cause has to be corrected before the switch is reset: combustion air, gas pressure, the burners and orifices, or the venting. Those are a technician’s job, and a cracked heat exchanger can be behind a rollout too. So if you find a popped rollout button, leave it and call us.
What not to do
Never jump or bypass a safety switch to get heat back. Each one is there to stop the furnace from burning gas when something is wrong, and the wrong thing is often exhaust, which carries carbon monoxide. Bryant’s manual is blunt about the rollout switch: do not jumper it. If a carbon monoxide alarm goes off, get everyone outside and read our CO alarm guide from there.
What a technician does
We measure the temperature rise across the furnace and the static pressure in the ducts, which tells us whether the airflow is the problem. Then we check the blower wheel, the motor and capacitor, the gas input and the switch itself. On a rollout we look at the burners, the heat exchanger and the venting before anything gets reset.
What it costs to have us look
A repair visit starts with a flat $99 diagnostic, and you get the price of the fix before we touch anything. Our Bryant page has more on the Bryant equipment we work on. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler.
Related: every Bryant furnace code, dirty blower wheels, furnace short cycling and Carrier code 33, which reads the same way. Other brands are on our error code and warning light guide.
Every code meaning here comes from Bryant’s own documents: 915SB installation instructions and 916SA installation instructions.
Call or book
Call (703) 997-9757 and tell us the code you counted, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
What does code 33 mean on a Bryant furnace?
A switch in the limit circuit opened: the main limit, which trips on overheating, or a rollout switch, which trips on flame in the wrong place. Most of the time it’s airflow.
What’s the difference between Bryant code 33 and code 13?
33 means the limit circuit is open right now. 13 means it stayed open more than 3 minutes, so the board locked out and will wait 3 hours before it tries again.
Can a dirty filter cause code 33?
Yes. It’s the first thing Bryant lists. A clogged filter cuts the airflow and the furnace runs hot enough to open the limit.
Should I reset the rollout switch myself?
No. Bryant says the cause has to be fixed before it’s reset, and the causes are venting, combustion air or the burners. Leave it and call.
How much does it cost to fix code 33?
The visit starts with a flat $99 diagnostic, and you get the price of the repair before any work starts.
