The short answer
Code 31 on a Bryant furnace in Northern Virginia means the high-heat pressure switch didn’t close, or it closed and opened again. Code 32 is the same thing on the low-heat switch. A pressure switch only closes once the inducer, the small fan on top, pulls enough draft through the vent, so the furnace won’t light until it does. The usual causes are a plugged condensate drain, a blocked vent, a kinked or water-filled tube, or an inducer that’s wearing out.
What you’ll notice
- The inducer starts and runs, but the burners never light.
- The furnace tries, quits, waits and tries again.
- The light flashes 3 short and 1 long (31) or 3 short and 2 long (32), or the display shows 31.2 or 31.3.
- It’s fine for days and throws the code on the coldest night, when the furnace makes the most condensate water.
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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 31 is 3 short and 1 long, then a pause before it repeats. The other has the same light plus a small display that shows three digits, like 31.2: 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 32, if the low-heat switch stays open more than 5 minutes, the board shuts the inducer off for 15 minutes and then tries again. On the display boards, 31.3 means the board tried three times and the high-heat switch never closed, so it locked out. Code 23 is the opposite problem: a switch that didn’t open when the inducer stopped, which points at a stuck switch or a blocked tube.
What causes code 31 and 32
These are the checks in Bryant’s 915SB manual, 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? |
|---|---|---|
| Condensate drain plugged | Gurgling, water around the furnace, a full condensate pump that isn’t running | Yes: the hose and the pump |
| Vent blocked or holding water | Leaves, a nest, snow or ice at the pipe ends outside; a sagging pipe run | Yes: the pipe ends |
| Pressure switch tubing | The small rubber tube to the switch is kinked, cracked, off its port or holding water | Look, and push it back on if it slipped |
| Inducer motor | Louder than it used to be, slow to spin up, grinding | No: we measure it |
| Wind | The code shows up only on gusty days | No: the pipe ends may need a change |
| Low inducer voltage, gas pressure, combustion air, vent size | Mostly on new installs or after a remodel | No: these get measured |
What you can safely check
- Go outside and look at the two white PVC pipe ends. Clear leaves, snow or ice from around them, and don’t push anything into the pipe.
- Look at the condensate hose and pump beside the furnace. Our condensate drain guide walks through it.
- Find the small rubber tube on the pressure switch. If it slipped off, push it back on snugly. If it’s cracked or full of water, leave it for us.
- Count the code, turn the furnace switch off for 30 seconds and back on, and let it try once.
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. And don’t buy a new pressure switch on a hunch. A new switch on a furnace with a plugged drain trips exactly like the old one. If you smell gas, don’t flip any switches: leave the house and call your gas company or 911 from outside.
What a technician does
Bryant’s manual has a simple test: with the inducer unplugged and a call for heat, the igniter must not glow and the board should flash 31. That proves the switch opens when it should. Then we put a manometer on the switch and compare the draft the inducer pulls with the setting on the switch. That one reading sorts out the drain, the vent, the tube, the inducer and the switch.
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, how a furnace pressure switch works, Carrier code 31, which reads the same way, and furnace short cycling. 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 31 mean on a Bryant furnace?
The high-heat pressure switch didn’t close, or it reopened. The furnace won’t light until the inducer pulls enough draft through the vent to close it.
What’s the difference between Bryant code 31 and 32?
31 is the high-heat (secondary) pressure switch and 32 is the low-heat (main) pressure switch. The list of causes is the same.
Can a clogged condensate drain cause code 31?
Yes. Water backing up into the furnace keeps the switch from closing. It’s one of the first things to check, especially on a cold night.
Should I replace the pressure switch myself?
No. The switch itself is rarely the problem, and a new one trips the same way if the drain or vent is the cause. We measure the draft first.
How much does it cost to fix code 31?
The visit starts with a flat $99 diagnostic, and you get the price of the repair before any work starts.
