Carrier Furnace LED Flash Codes: Complete Fault Code Guide

Quick Answer

Carrier furnaces signal problems through LED blink codes on the control board. Each code is a combination of short and long blinks.

Carrier furnaces signal problems through LED blink codes on the control board. Each code is a combination of short and long blinks. Common codes include 3 short 3 long (Code 33, pressure switch), 1 short 3 long (Code 13, limit lockout), 3 short 1 long (Code 31, gas valve), 3 short 4 long (Code 34, ignition proving failure), 1 short 2 long (Code 12, blower motor), and 1 short 4 long (Code 14, ignition lockout). Match your LED blink pattern to the code list to identify your fault and follow the specific repair guide.

CarrierFurnace

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Not seeing HUB on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

pressure switch fault, 3-3 blink pattern

3 Short 3 Long

overheating, limit switch tripped

gas valve not opening

flame not detected after ignition

blower motor not starting

ignition lockout requiring manual reset

fault code reset procedure

RESET

LED flash code error

GoodmanHUB

About These Carrier Furnace Error Codes

Carrier furnaces communicate all faults via LED flash codes on the control board. Count the short blinks, then the long blinks to read the code number.

Most Common Error Codes

Pressure switch failure or blocked condensate drain (Code 33)40%

Overheating due to dirty air filter or restricted airflow (Code 13)24%

Gas valve fault or supply issue (Code 31)14%

Blower motor or run capacitor failure (Code 12)12%

Failed flame sensor or hot surface ignitor (Code 34)10%

Symptoms You May Notice

Furnace not heating
Furnace starts then shuts off
LED on control board blinking in a repeating pattern
No ignition or flame
Blower running but no heat

Tools Required for Diagnosis

FlashlightFurnace owner's manual

How to Identify Your Error Code

Locate the control board LED through the furnace sight glass or

Locate the control board LED through the furnace sight glass or small observation window on the lower cabinet door. Watch the LED for one full blink cycle.

Count the short blinks before the pause

Cross-reference your code with the list

Frequently Asked Questions

How do I read the LED blink code on my Carrier furnace?

Watch the LED on the control board through the observation window or sight glass. It blinks in groups separated by a pause. Count the short blinks before the pause (first digit) and the long blinks after the pause (second digit). For example, 3 short blinks followed by 3 long blinks equals Code 33.

Where is the control board LED on a Carrier 59TP6 or 59MN7?

On most Carrier 59-series furnaces the LED is visible through a small sight glass or observation port on the lower cabinet door without opening the cabinet. If you cannot see it, open the lower service door after turning off power to expose the control board directly.

Will the Carrier furnace LED code clear on its own after repair?

Yes. After the fault condition is resolved the control board clears the code on the next successful heating cycle. You can also manually clear it by cycling power at the circuit breaker for 30 seconds.

What is the most common Carrier furnace LED fault code?

Code 33 (3 short + 3 long blinks) is the most frequently reported Carrier furnace fault. It indicates a pressure switch circuit open, most often caused by a clogged condensate drain line rather than an actual switch failure.

My Carrier furnace LED is blinking but I do not see my code number listed. What should I do?

Some Carrier models use additional codes not covered in this guide. Download the installation manual for your specific model number from carrier.com and cross-reference the full code table. If the pattern is 2 blinks repeating without a pause, the board is in normal standby mode, not a fault.

Related Carrier Furnace Error Codes

Code: 3 Short 3 LongCarrier Furnace Code 33: Pressure Switch Fault Code: 13Carrier Furnace Code 13: Limit Device Fault Lockout Code: 31Carrier Furnace Code 31: Gas Valve Failure Code: 34Carrier Furnace Code 34: Ignition Proving Failure Code: 12Carrier Furnace Code 12: Blower Wheel Motor Fault Code: 14Carrier Furnace Code 14: Ignition Lockout After Multiple Failures Code: RESETHow to Reset a Carrier Furnace and Clear LED Fault Codes

Same Fix on Other Brands

Goodman furnaceGoodman Furnace Error Codes Guide

Models Known to Experience HUB Errors

This repair applies to most Carrier furnaces with this error code. Common model numbers include:

59TP6, 59MN7, 59SP5, 59TP6A, 58PAV

Last verified for technical accuracy on March 14, 2026