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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Code	Description	Common Cause	Fix
1 flash	No previous error code stored	Normal condition after power reset	No action needed
2 slow	Abnormal flame proving signal (flame without gas valve)	Gas valve leaking through, faulty flame sensor, or short in flame sensor wiring	Check gas valve for leak-through, inspect flame sensor wiring for shorts, replace gas valve if leaking
2 fast	Control lockout (retry limit exceeded)	Failed to ignite after multiple attempts, weak flame signal, or gas supply issue	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	Pressure switch contacts welded, faulty pressure switch, or wiring short	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	Blocked condensate drain, cracked inducer housing, failed inducer motor, blocked flue/intake, or bad pressure switch	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	Dirty filter restricting airflow, blocked return air, failed blower motor, or oversized gas input	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	Blown 3A fuse on control board, short in low-voltage wiring, or transformer failure	Check 3A fuse on board, inspect thermostat wiring for shorts, check transformer output (24V)
Steady ON	Normal operation, no call for heat	Normal standby	No action needed
Steady OFF	No power to control board	No 24V power, blown transformer, or open safety switch	Check transformer output, check all safety switches in series, verify line voltage to furnace
Rapid flash	Line voltage polarity reversed	Hot and neutral swapped at furnace or incorrect wiring	Check polarity at furnace junction box, swap hot and neutral if reversed, check outlet/disconnect wiring

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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