The short answer
If your Bryant furnace in Northern Virginia lights for a few seconds and then shuts off, suspect the flame sensor first. It’s a thin metal rod that sits in the flame, and the board reads a tiny electric current through it to prove the burners lit. When a film builds up on the rod, the current drops, the board can’t prove the flame, and it closes the gas. The light flashes 34, and after enough failed tries, 14 for a lockout.
What you’ll notice
- The inducer starts, the igniter glows, the burners light, and they go out within a few seconds.
- The furnace tries again, up to four times in all.
- The amber light flashes 3 short and 4 long for 34, or 1 short and 4 long for 14 once it gives up. A board with a display shows 34.1 or 14.1.
- The house cools off while the furnace sits quiet, then it starts trying again on its own.
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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 34 is 3 short and 4 long, then a pause before it repeats. The other has the same light plus a small display that shows three digits, like 34.1: 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 codes 34 and 14 mean on a Bryant
Bryant’s 916SA furnace, the one with the display, splits each code with a third digit. The 915SB, with only the light, flashes the plain 34 or 14. The meaning is the same on both.
Swipe to see all columns →
Swipe to see all columns →
| Code | What Bryant’s 916SA manual says |
|---|---|
| 34.1 | Ignition failed on all four tries: the board never sensed a flame |
| 34.2 | The flame was lost before the blower on-delay finished |
| 34.3 | The flame was lost after the blower came on |
| 14.1 | Ignition lockout after 4 failed tries in a row |
| 14.2 | The flame dropped out 3 times after 70 seconds of heating |
| 14.3 | Lockout after 7 losses of flame |
On the display board, a technician can also scroll to FLt and see the last 7 faults, which tells us whether this is the first 34 or the tenth.
How the lighting sequence works
On a call for heat, the inducer runs a 15-second prepurge to clear the heat exchanger, the igniter warms up for about 17 seconds, and the gas valve opens. The board has to sense a flame within 2 seconds or it closes the gas, and it tries up to 3 more times. After the fourth failed try it locks out. A lockout clears itself after 3 hours, or right away with a short break in the power, which is what flipping the furnace switch does.
What makes a flame sensor fail
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Swipe to see all columns →
| Cause | What’s going on |
|---|---|
| A coating on the rod | Oxide and dust build a film that weakens the signal. By far the most common one. |
| A loose or worn wire | The single wire from the board to the rod corrodes or works loose at its terminal. |
| A cracked insulator | The white porcelain at the base cracks and lets the signal leak to the metal. |
| A poor ground | The signal returns through the burners and the furnace frame. Rust or a loose ground wire breaks that path. |
| A weak or lifting flame | Low gas pressure or dirty burners keep the flame off the rod, so it never gets a full signal. |
| Reversed polarity | Hot and neutral swapped at the furnace. The light flashes rapidly instead of a code. |
What a good signal looks like
Carrier, which makes Bryant, gives the numbers in its 58SC0A installation instructions: a healthy sensor reads 4.0 to 6.0 microamps, and the board needs at least 0.5 to call it a flame. A coated rod can read just over the minimum and light most of the time, then miss on the next cycle, which is why the problem comes and goes.
Cleaning it, and why it’s a technician’s step
Bryant’s maintenance steps say to clean the flame sensor with fine 0000 steel wool, and never sandpaper or emery cloth, which scratch the rod and leave grit that brings the coating back faster. Bryant writes those steps for a qualified service technician. The rod sits right beside the igniter, which is brittle and breaks if you bump it, and the burner compartment is part of the gas system. A cracked igniter turns a cleaning into a part, and a sensor that’s clean but still reads low is pointing at something else in that table.
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. Flipping the switch over and over doesn’t fix a dirty sensor either. It only starts another 4 tries. 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
We watch a full lighting sequence, read the flame signal in microamps before and after cleaning, and check the wire, the insulator, the ground, the flame itself and the gas pressure. If the signal comes back to the normal range, the sensor stays. If it doesn’t, we replace it, and you get the price before the part goes in.
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.
- Every Bryant furnace code and what to do
- The Carrier flame sensor, the same part on Carrier furnaces
- Furnace flame sensor problems on any brand
- How to reset a Bryant furnace, and when not to
- Error codes and warning lights by brand
Every code meaning and the cleaning step 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
Why does my Bryant furnace light and then shut off?
Most often the flame sensor. The burners light, the board can’t read enough current through the sensor to prove the flame, and it closes the gas within seconds. The light flashes 34. Low gas pressure, a poor ground or a cracked insulator on the sensor do the same thing.
What does code 14 mean on a Bryant furnace?
Ignition lockout. The furnace failed to light or hold a flame too many times and stopped trying. It resets itself after 3 hours, but the cause is still there, and it’s usually the flame sensor or the igniter.
Can I clean a Bryant flame sensor myself?
Bryant’s steps say fine 0000 steel wool, never sandpaper, and they’re written for a technician. The igniter beside the sensor is brittle and the burners are part of the gas system, so if you’re not comfortable with the power and gas off and a part in your hand, have us do it.
Is a dirty flame sensor dangerous?
Not by itself. It’s a safety part, and when it can’t prove the flame it shuts the gas off, which is its job. The risk is in what comes next: bypassing it, or resetting the furnace over and over. Leave the safety in place and get it cleaned or replaced.
How much does it cost to have a Bryant flame sensor looked at?
A repair visit starts with a flat $99 diagnostic, and you get the price of the fix before any work starts. Our heating check is $67 per system, through December 31.
