Furnace Fault Codes

What your furnace's blinking light or error code actually means

Most furnaces report faults by flashing a status LED a set number of times, or by showing a code on a small display. Each entry below explains what a given signal means, what normally causes it, what you can safely check yourself, and when it needs a licensed technician.

Goodman and Amana

• 1 flash — Lockout after too many failed ignition attempts
• 2 flashes — Pressure switch is closed when it should be open
• 3 flashes — Pressure switch will not close
• 4 flashes — High limit switch is open — the furnace is overheating
• 5 flashes — Flame detected when no flame should be present
• 6 flashes — Rollout switch has tripped
• 7 flashes — Flame signal is too weak
• 8 flashes — Igniter circuit fault, most often caused by poor grounding
• 9 flashes — High stage pressure switch stuck open
• rapid flashing — Reversed 115 volt polarity, a grounding problem, or an open igniter circuit
• LED off — No power to the furnace, or an internal control fault
• continuous on — Normal operation — no fault stored
• 6 flashes — Rollout limit open, or control module fuse blown

Goodman and Amana display codes

• E0 — Lockout after too many failed ignition attempts
• E1 — Low stage pressure switch closed at the start of the heating cycle
• E2 — Low stage pressure switch stuck open
• E3 — High limit switch is open — the furnace is overheating
• E4 — Flame detected when no flame should be present
• E5 — Low voltage fuse is open
• E6 — Flame signal is too weak
• E7 — Igniter fault or improper grounding
• E8 — High stage pressure switch closed at the start of the heating cycle
• E9 — High stage pressure switch stuck open
• EA — Reversed 115 volt polarity
• Ed — Rollout switch has tripped
• EC — Inducer motor overcurrent
• EF — Auxiliary switch or input is open

Goodman and Amana blower codes

• b0 — Blower motor is not running
• b1 — Blower communication error
• b2 — Blower motor horsepower mismatch
• b3 — Blower motor operating at a power, temperature, or speed limit
• b4 — Blower motor current trip or lost rotor
• b5 — Blower motor locked rotor
• b6 — Blower motor over or under voltage trip, or over temperature trip
• b7 — Incomplete parameters sent to the motor
• b9 — Low indoor airflow
• d0 — Data not yet on network
• d4 — Invalid memory card data

Carrier and Bryant

• Status code 11 — No previous code stored
• Status code 12 — Blower running after power up
• Status code 13 — Limit circuit lockout
• Status code 14 — Ignition lockout
• Status code 21 — Gas heating lockout — will not reset automatically
• Status code 22 — Abnormal flame-proving signal — flame detected with the gas valve closed
• Status code 23 — Pressure switch did not open
• Status code 24 — Secondary voltage fuse is open
• Status code 31 — Pressure switch did not close, or reopened
• Status code 33 — Limit circuit fault — a limit or flame rollout switch is open
• Status code 34 — Ignition proving failure
• Status code 45 — Control circuitry lockout
• LED continuously off — No power reaching the control
• LED rapid flashing — Line voltage polarity reversed
• Status code retrieval, amber LED controls — How to read stored status codes on Carrier amber LED boards

Trane and American Standard

• 2 flashes — System lockout — retries or recycles exceeded
• 3 flashes — Draft pressure error
• 4 flashes — Open high limit device
• 5 flashes — Flame sensed when no flame should be present
• 6 flashes — 115 volt AC power reversed, or poor grounding
• 7 flashes — Gas valve circuit error
• 8 flashes — Low flame sense signal
• 9 flashes — Ignitor circuit problem, or low voltage between neutral and 24 volt common
• Flashing slow — Normal — no call for heat
• Flashing fast — Normal — call for heat
• Continuous on — Replace the integrated furnace control
• Continuous off — Check power

Rheem, Ruud and Weather King

• 1 blink — Soft lockout, one hour
• 2 blinks — Pressure switch failure — switch remains open
• 3 blinks — Limit switch open
• 4 blinks — Pressure switch failure — switch remains closed
• 5 blinks — Twinning circuit failure

Goodman GMEC96 and Amana AMEC96 colour codes

• 1 red flash — Flame sensed when no flame should be present
• 2 red flashes — Pressure switch stuck closed, or an inducer error
• 3 red flashes — First stage pressure switch stuck open, or an inducer error
• 3 double red flashes — Second stage pressure switch stuck open, or an inducer error
• 4 red flashes — Open limit switch
• 5 red flashes — Open rollout switch, or open fuse detected
• 6 red flashes — Pressure switch cycle lockout
• 7 red flashes — External lockout — ignition retries exhausted
• 8 red flashes — External lockout — recycles exhausted
• 9 red flashes — Grounding problem or reversed polarity
• 10 red flashes — Gas flow detected with a call for heat
• 11 red flashes — Limit switch open due to blower failure
• 12 red flashes — Ignitor relay failure
• rapid amber flashing — Low flame sense current
• rapid red flashing — Twinning error
• solid red — Internal control fault, gas valve error, microprocessor or frequency check failure
• 3 amber flashes — Second stage heat called with no first stage call
• 4 amber flashes — Cooling called with no fan call
• 1 amber flash — Normal operation — first stage heat
• solid green — Standby — powered, no call

Lennox communicating alert codes

• Alert code 200 — Rollout limit switch open
• Alert code 204 — Check gas valve
• Alert code 205 — Gas valve relay contact closed
• Alert code 206 — Gas valve second stage relay fault
• Alert code 207 — Hot surface igniter sensed open
• Alert code 223 — Low pressure switch open
• Alert code 226 — High pressure switch stuck closed
• Alert code 227 — Low pressure switch open in run mode
• Alert code 228 — Inducer calibration issue
• Alert code 229 — Ignition on high fire — information only
• Alert code 240 — Low flame current in run mode
• Alert code 250 — Flame out of sequence — still present
• Alert code 251 — Primary limit switch open
• Alert code 252 — Discharge air temperature high
• Alert code 270 — Flame failed to ignite — Watchguard
• Alert code 271 — Low pressure switch open — Watchguard
• Alert code 272 — Low pressure switch open in run mode — Watchguard
• Alert code 273 — Flame failed in run mode — Watchguard
• Alert code 274 — Primary limit switch open more than three minutes — Watchguard
• Alert code 201 — Indoor blower motor communication lost
• Alert code 202 — Blower motor and unit size mismatch
• Alert code 203 — Invalid or unset unit size code

York, Luxaire and Coleman

• Fault code retrieval — How to read and clear stored fault codes on York UTEC boards
• Green heartbeat — Normal operation, no call for heat, no active errors
• Amber heartbeat — Normal operation with a call for heat
• 1 red flash — Flame sensed with the gas valve off
• 3 red flashes — Pressure switch open, or first stage pressure switch open
• 3 double red flashes — Second stage pressure switch stuck open
• 5 red flashes — Open rollout switch
• 6 red flashes — Pressure switch cycle lockout
• 7 red flashes — One hour lockout after ignition retries
• 8 red flashes — Lockout on recycles, flame dropouts
• 9 red flashes — Grounding, reversed polarity, or reversed transformer leads
• 10 red flashes — Gas valve energised with no call for heat
• 11 red flashes — Limit switch open more than five minutes — blower failure
• 12 red flashes — Open hot surface igniter
• Rapid red flashing — Twinning error or incorrect 24 volt phasing
• Rapid amber flashing — Low flame sense current
• Solid LED — Control fault detected
• Steady off — No power to the board, or control failure
• 2 red flashes — Pressure switch stuck closed, or an inducer error
• 4 red flashes — Open high limit switch
• 3 amber flashes — Second stage heat present with no first stage call
• 4 amber flashes — Cooling called with no fan call
• 2 amber flashes — Normal operation with a call for second stage heat

Reading the codes

• Reading a furnace fault code — How to find, count, and interpret the diagnostic light before looking anything up
• When to stop and call someone — The furnace conditions that are not a diagnosis problem

Goodman modulating display codes

• IF — Internal control fault
• Ft — Field test mode
• On — Normal operation
• F — Continuous fan
• A — Airflow display, followed by the CFM value
• H — Gas heat demand, followed by the demand percentage
• HI — High heat at 100 per cent demand
• LO — Low stage heat
• dF — Defrost demand
• P1 — Low stage compressor, heating mode
• P2 — High stage compressor, heating mode
• C1 — Low stage compressor, cooling mode
• C2 — High stage compressor, cooling mode