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Carrier Error Codes & Fault Codes

Complete LED flash code reference for Carrier, Bryant, and Payne furnaces. Bookmark this page for quick field lookups.

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CodeDescription
1 flashNo previous error code stored
2 slowAbnormal flame proving signal (flame without gas valve)
2 fastControl lockout (retry limit exceeded)
3 slowPressure switch stuck closed
3 fastPressure switch stuck open / not closing
4 slowOpen high temperature limit switch
4 fastOpen fuse / internal fault
Steady ONNormal operation, no call for heat
Steady OFFNo power to control board
Rapid flashLine voltage polarity reversed

Detailed Code Reference

1 flash
No previous error code stored
Cause: Normal condition after power reset
Fix: No action needed
2 slow
Abnormal flame proving signal (flame without gas valve)
Cause: Gas valve leaking through, faulty flame sensor, or short in flame sensor wiring
Fix: Check gas valve for leak-through, inspect flame sensor wiring for shorts, replace gas valve if leaking
2 fast
Control lockout (retry limit exceeded)
Cause: Failed to ignite after multiple attempts, weak flame signal, or gas supply issue
Fix: Check gas supply pressure, clean flame sensor with emery cloth, check igniter gap and condition, reset board (power cycle)
3 slow
Pressure switch stuck closed
Cause: Pressure switch contacts welded, faulty pressure switch, or wiring short
Fix: Disconnect hose from pressure switch (should open), replace pressure switch if stuck, check for wiring short to ground
3 fast
Pressure switch stuck open / not closing
Cause: Blocked condensate drain, cracked inducer housing, failed inducer motor, blocked flue/intake, or bad pressure switch
Fix: Check condensate drain for blockage, inspect inducer motor operation, check flue pipe for blockage, verify pressure switch hose is connected and clear, test pressure switch with manometer
4 slow
Open high temperature limit switch
Cause: Dirty filter restricting airflow, blocked return air, failed blower motor, or oversized gas input
Fix: Check and replace air filter, verify all registers are open, check blower motor operation and capacitor, verify gas pressure is correct
4 fast
Open fuse / internal fault
Cause: Blown 3A fuse on control board, short in low-voltage wiring, or transformer failure
Fix: Check 3A fuse on board, inspect thermostat wiring for shorts, check transformer output (24V)
Steady ON
Normal operation, no call for heat
Cause: Normal standby
Fix: No action needed
Steady OFF
No power to control board
Cause: No 24V power, blown transformer, or open safety switch
Fix: Check transformer output, check all safety switches in series, verify line voltage to furnace
Rapid flash
Line voltage polarity reversed
Cause: Hot and neutral swapped at furnace or incorrect wiring
Fix: Check polarity at furnace junction box, swap hot and neutral if reversed, check outlet/disconnect wiring

Frequently Asked Questions

What does Carrier error code 3 fast flashes mean?

Three fast flashes on a Carrier furnace means the pressure switch is stuck open or not closing. This is commonly caused by a blocked condensate drain, cracked inducer housing, failed inducer motor, blocked flue or intake, or a bad pressure switch. Start by checking the condensate drain and inducer motor operation.

How do I reset a Carrier furnace lockout?

To reset a Carrier furnace lockout (2 fast flashes), power cycle the furnace by turning it off at the breaker or disconnect for 30 seconds, then restoring power. Before resetting, diagnose the root cause: check gas supply pressure, clean the flame sensor with emery cloth, and inspect the igniter.

What does a steady LED light on a Carrier furnace mean?

A steady ON LED on a Carrier furnace indicates normal operation with no call for heat. The system is in standby mode and waiting for the thermostat to call for heating. This is not an error condition.

Do Bryant and Payne use the same error codes as Carrier?

Yes. Carrier, Bryant, and Payne are all manufactured by Carrier Global. They share the same control boards and LED flash code system, so the error codes listed here apply to all three brands.

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