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ErrBase

Carrier Furnace Error Codes

All Carrier furnace error codes with step-by-step troubleshooting, multimeter specs, and OEM part numbers.

11 error codes

CodeMeaning
12Code 12 means the blower motor didn't reach operating speed within the expected window after a heat call, or it stalled out mid-cycle. The control board's watching motor performance constantly, and when the blower doesn't respond the way it should, it locks out and throws this code.
moderateintermediate
13Code 13 on a Carrier furnace means the high limit switch or a secondary safety limit (rollout switch) has tripped. These switches are thermal cutoffs that open when the furnace detects dangerously high temperatures inside the heat exchanger or combustion chamber. The furnace shuts down completely to prevent damage or fire.
highintermediate
13Code 13 means the furnace control board counted the high limit switch or flame rollout switch opening too many times in one heating cycle. The heat exchanger's getting hotter than it should. That's the board shutting things down before something actually breaks.
highintermediate
14Code 14 on a Carrier furnace is an extended ignition lockout triggered by repeated failed ignition attempts. The control board has tried to light the furnace multiple times, typically 3 cycles, each time resulting in Code 34 (ignition proving failure), and has now locked out entirely. The furnace won't attempt another ignition cycle until it's manually reset.
highintermediate
3 Short 3 LongCode 33 on a Carrier furnace means the pressure switch circuit is stuck open. The pressure switch is a safety device that's supposed to verify the inducer motor has created enough negative draft pressure before it lets the gas valve open. When the switch doesn't close during a heating cycle, the furnace shuts down to prevent unburned gas from accumulating.
highintermediate
31Code 31 on a Carrier furnace indicates the gas valve is not opening or is closing prematurely during a heating cycle. The control board sends a 24VAC signal to the gas valve solenoid at the appropriate time in the sequence, but the valve either fails to open or opens and then closes before the ignitor and flame sensor complete their cycle.
highadvanced
31Carrier error code 31 indicates that the pressure switch did not close or has opened during a cycle. This safety mechanism ensures the inducer motor is creating enough vacuum to safely exhaust combustion gases before the furnace is allowed to ignite.
highintermediate
33Code 33 indicates a Limit Circuit Fault. The furnace's high limit switch has opened, indicating overheating, and because this happened three times in a row, the unit has entered a hard lockout for safety.
highmoderate
34Code 34 means the furnace tried to light but the flame sensor didn't report back a stable flame within the proving window, usually 7-10 seconds after the gas valve opens. The control board cuts gas immediately as a safety measure. One attempt on most models, then lockout.
highintermediate
HUBThis hub covers all Carrier furnace LED flash fault codes. Carrier furnaces use a single LED on the control board that blinks in short and long patterns to communicate fault codes. Counting the blink sequence identifies the specific fault.
lowbeginner
RESETResetting a Carrier furnace clears the stored fault code from the control board and allows the furnace to attempt a new startup sequence. There are two levels of reset: a soft reset via the thermostat and a hard reset via the circuit breaker. A third manual reset is required for Code 13 rollout lockouts and is specific to the physical rollout switch inside the cabinet.
lowbeginner