Carrier furnace codes are two digits flashed on a light behind the window in the lower door: count the short flashes for the first digit, then the long flashes for the second. Code 31 is the pressure switch, 33 a limit or rollout, 13 a limit lockout, 34 a flame that wasn’t proven. Bryant and Payne (now WeatherMaker) print the same codes. A repair starts with our $99 diagnostic; a flame sensor cleaning is $95 to $180 and a control board $550 to $1,180.
Our Carrier repair page has every repair price and what we’d recommend if it’s done.
Carrier furnace flash codes
| Code | What it means | What it usually takes |
|---|---|---|
| Rapid flashing | Line voltage polarity reversed; it won’t heat | A wiring fix |
| 11 | No previous code (stored codes clear after 72 hours) | Nothing |
| 12 | Blower on after power up | Normal |
| 13 | Limit lockout: a limit, rollout or vent switch open over 3 minutes; resets after 3 hours | Airflow first; a rollout needs a look |
| 14 | Ignition lockout: 4 tries, no proven flame; resets after 3 hours | Gas, igniter or flame sensor |
| 21 | Gas heating lockout | Turn off power 5 minutes, retry; then call |
| 22 | Flame proved with the gas valve off | Call |
| 23 | Pressure switch didn’t open | A blocked tube or a stuck switch |
| 24 | 24-volt fuse open | A short in the thermostat or low voltage wiring |
| 31 | Pressure switch didn’t close or reopened | Drain, vent, tube or inducer |
| 32 | Low-heat pressure switch didn’t close (two-stage) | Drain, vent, tube or inducer |
| 33 | A limit, rollout or vent switch is open | Airflow, venting or a rollout |
| 34 | Ignition proving failure | Usually a flame sensor cleaning |
| 41 | Blower motor fault | The blower motor or its control |
| 45 | Control circuitry lockout | Cycle power; if 45 repeats, a new board |
From Carrier’s 58SC0A installation instructions.
Newer Carrier furnaces show a code like 13.1
Current Carrier, Bryant and WeatherMaker furnaces print a three-character code on a small display: the first two digits are the main code above, the third narrows it down. 13.1 is a limit lockout, 14.1 an ignition lockout, 32.1 the main pressure switch open, 34.1 an ignition fault over four tries, 10.1 a polarity fault (Carrier 59SC6A manual).
Code 31: the pressure switch
Carrier’s own checklist for a pressure switch that won’t close: a plugged condensate drain, water sitting in the vent pipe, a blocked pressure tube, and a failing inducer motor. On a high-efficiency furnace the drain is the usual one, and clearing it with a trap and float switch is $175 to $420.
Codes 33 and 13: limits and rollout
33 means one of the safety switches is open right now; 13 means it stayed open over three minutes and the furnace locked out. A dirty filter or a dust-packed blower wheel ($300 to $440 to clean) trips the limit. A rollout switch is different: it trips when flame rolls out of the burners, so it needs a technician to find out why before anyone resets it.
Code 34: the flame sensor
The burners lit but the board didn’t see the flame, and Carrier’s fix list starts with cleaning the flame sensor ($95 to $180). After three more tries it becomes code 14.
Carrier furnace code questions people ask us
What does code 33 mean on a Carrier furnace?
A limit, rollout or vent switch is open. Start with the filter and airflow. If it’s the rollout switch, call: the diagnostic is $99.
What does code 31 mean on a Carrier furnace?
The pressure switch didn’t close. Usually a plugged condensate drain, water in the vent pipe, a blocked pressure tube or a failing inducer.
How do I read Carrier furnace flash codes?
Short flashes are the first digit, long flashes the second: three short and one long is 31.
Does Bryant use the same codes as Carrier?
Yes. Bryant is a Carrier company, and their 2026 furnace manuals print the identical table. See the Carrier repair page for prices.
