Carrier Furnace Codes: What Each Flash Code Means (and Bryant)

Carrier gas furnaces report faults with a status light on the control board, which you read through the small sight glass in the blower access door. Each code is a two-digit number: the first digit is the number of short flashes and the second is the number of long flashes, so 3 short and 4 long is code 34. Write the code down before you touch anything, then switch the furnace power off for 30 seconds and back on, once. If the code comes back, the furnace needs a technician.

The table below comes from Carrier's own installation and service manual for its 58SC0A and 58SC1A single-stage furnaces. Bryant prints the same table for its 810SA and 811SA furnaces, which we cover further down.

If you smell gas, stop here

A gas smell is not a code to look up. Leave the house, then call your gas supplier or 911 from outside or from a neighbor's home. Carrier's guide to a furnace that won't turn on says not to troubleshoot the furnace yourself if you suspect a leak, and to evacuate and call from a safe place if you smell rotten eggs or a carbon monoxide alarm sounds.

How to read the status light

Carrier's 58SC0A/58SC1A installation and service manual says the status light can be viewed at the sight glass in the blower access door. Its steps have you remove the outer access door first, then look through the glass in the blower access door behind it. The light does one of four things:

• Stays on: the control has 24-volt power. That's normal.
• Stays off: no power is reaching the control.
• Flashes rapidly: the line voltage polarity is reversed and the furnace won't heat.
• Flashes a pattern: short flashes, then long flashes, then a pause. Count both.

Leave the inner blower door in place while you read the light. The manual explains that this door presses a switch that cuts power to the control when it comes off, and that on red-light boards a power interruption can also erase the stored code. You would lose the code you're trying to read.

Carrier furnace codes table

Codes and meanings below are from the 58SC0A/58SC1A manual's service label (Fig. 44) and troubleshooting guide (Fig. 51), put into plain English. The "what you can check" column only holds steps Carrier gives homeowners, from the same manual or Carrier's support page.

For anything marked "Yes", call a licensed technician. Most of those causes sit in the burner compartment, the gas valve or the venting.

Bryant furnace codes are the same on these models

Bryant is a Carrier brand, and the code tables match on the sister models we checked. Bryant's 810SA/811SA installation and service manual prints the same service label and the same troubleshooting guide, word for word, as Carrier's 58SC0A/58SC1A manual. Same codes, same meanings, same retrieval steps. If you have one of those Bryant furnaces, the table above is your table.

We didn't compare every Bryant and Carrier pair. If your Bryant has a different model number, check the service label on its blower door.

What to do for the common codes

Codes 13 and 33: limit circuit

Code 33 means a safety switch that watches for overheating, flame rollout or a blocked vent is open right now. The blower runs for at least 4 minutes to cool things down. If the switch stays open longer than 3 minutes, the code becomes 13 and the furnace locks out for 3 hours.

The first cause on Carrier's list is a dirty filter or a restricted duct system. Turn the power off, pull the filter and replace it if it's clogged. The manual calls for checking it every month. Our guide on how often to change a furnace filter covers sizes and types. The other causes, a loose blower wheel, a failed motor, a blocked vent or a tripped rollout switch, are technician work. Carrier says the rollout and blocked vent switches need a manual reset and that the cause has to be fixed first, so leave those alone.

Codes 14 and 34: ignition

Code 34 means the burners didn't light, or the flame sensor didn't see the flame. The control tries 3 more times. After 4 failed tries it shows code 14 and waits 3 hours.

Carrier's guide says to check first that the gas valve is turned on, and its support page tells homeowners to make sure the gas valve leading to the furnace is open. If another gas appliance is also dead, call your utility. Past that, the guide moves to the igniter, gas valve and flame sensor, which a technician should test. Carrier's furnaces in this manual use a hot surface igniter, so there is no pilot to relight; our furnace pilot light guide covers older furnaces that have one.

Code 31: pressure switch

Code 31 means the pressure switch that proves the draft fan is pulling air through the vent didn't close, or opened again. Carrier lists vent sizing, a restricted vent, excessive wind, low inducer voltage, a bad inducer motor or pressure switch, and loose or blocked tubing. None of those are homeowner fixes. Call a technician, and tell them if it happens on windy days.

Code 45: control lockout

The manual's own instruction is to reset power to clear the lockout and to replace the control if the code repeats. Switch the furnace off at its power switch, wait, and switch it back on. If 45 comes back, the board likely needs replacing.

Code 24 and rapid flashing

Code 24 means the 3-amp fuse on the board has blown because something shorted the 24-volt wiring, which includes the thermostat wires. Rapid flashing means the power wiring is reversed. Both need a technician to find the fault, not just swap a part.

Two-stage models add more codes

Codes differ by series, so check the label on your own furnace. Carrier's 58TN0A/58TN1A two-stage variable-speed manual uses the same short-and-long flash system and most of the same codes, but adds these and changes the meaning of 31:

On this model, code 13 can also mean 10 limit trips in a row during high heat.

Recalling the last stored code

The light may have stopped flashing by the time you look. Carrier's boards store the last code, and the manuals give a recall procedure, but it's written for technicians.

On the 58SC0A/58SC1A, the recall is done with power on and no call for heat: a technician briefly disconnects one wire on the draft safeguard switch until the light goes out, then reconnects it. The light then flashes the stored code 4 times, or code 11 if there's no fault history. The manual warns that holding the wire off longer than 4 seconds starts the blower and overwrites the code with 33. The two-stage 58TN0A stores up to 7 codes and recalls them with a setup switch on the board instead. Either way it means working on a live control, so leave recall to the technician and read the current code through the sight glass yourself.

Models this covers

• Carrier 58SC0A and 58SC1A, 80% single-stage: main table.
• Bryant 810SA and 811SA: same label and guide as the 58SC0A/58SC1A.
• Carrier 58TN0A and 58TN1A, 80% two-stage: the second table.

We could not open Carrier's condensing 59-series manuals (such as the 59SC5) when we wrote this, so we haven't listed their codes. On the models above, the code chart is printed on the service label on the blower access door, and the model number is on the unit's rating plate. If your furnace won't start at all and shows no code, work through our furnace won't turn on checklist. If it runs but blows cold air, see why a furnace blows cold air. For the other brands, we also have Goodman furnace error codes, Lennox furnace error codes and Trane furnace error codes.

Before you call, write down the model number, the code and what the furnace does when the thermostat calls for heat. That gives the technician a head start.