Goodman Furnace Blink Codes: 1–9 Flashes — What Each Code Means & How to Fix

Common Symptoms

• LED on the control board blinking in a repeated flash pattern
• Furnace not heating or locking out after multiple attempts
• Furnace starts then shuts off within seconds
• Inducer motor running but no flame appears
• Furnace completely unresponsive — LED blinks continuous fast pattern

Most Likely Causes

1. 1

   2 Flashes — System Lockout (Retry Limit Exceeded)

   The furnace attempted ignition 3–5 times without proving a stable flame and entered hard lockout. The underlying fault could be a failed igniter, dirty flame sensor, gas supply issue, or faulty gas valve. The lockout itself is not the fault — it means the board saw repeated ignition failures. Diagnose the ignition system first, then clear the lockout by power-cycling the furnace.

2. 2

   3 Flashes — Pressure Switch Fault

   The draft inducer pressure switch did not close (or close at the correct time) during startup. Causes: a blocked or cracked pressure hose, a failed inducer motor not building adequate draft, a clogged secondary heat exchanger on 90+ efficiency models, a waterlogged pressure tube, or a defective pressure switch. The furnace will not attempt ignition until the pressure switch closes.

3. 3

   4 Flashes — Open High Limit Device

   A high-limit switch has opened, indicating the heat exchanger reached an unsafe temperature. Root cause: severely clogged air filter, blocked return air, closed supply registers, a failed blower motor not moving enough air over the heat exchanger, or a cracked heat exchanger allowing combustion gases into the supply air. Replace the filter first — this accounts for the majority of 4-flash codes on Goodman furnaces.

4. 4

   6 Flashes — Ignition Failure (After 6 Attempts)

   The furnace made 6 consecutive ignition attempts without proving flame and locked out. Causes: a cracked or open-circuit hot surface igniter (test resistance — should be 40–90 ohms for silicon nitride igniters), a flame sensor coated with oxidation that cannot conduct the 1–2 microamp flame rectification signal, inadequate gas pressure at the manifold, or a faulty gas valve not opening on the ignition cycle.

5. 5

   7 Flashes — Low Flame Signal

   Flame is proven on ignition but the current through the flame sensor is below the threshold needed to keep the gas valve open. The furnace lights briefly then shuts off. Cause is almost always an oxidized flame sensor rod. Cleaning the sensor tip with fine emery cloth restores conductivity. If cleaning fails, check gas pressure and flame sensor wiring before replacing the sensor.

6. 6

   9 Flashes — Gas Valve Circuit Fault

   The control board detected an electrical fault in the gas valve circuit — either the valve coil is open or shorted, a wiring harness connection to the valve has failed, or the valve itself has an internal fault. Measure coil resistance across the valve terminals with power off: most Goodman gas valve coils read 20–60 ohms. OL indicates the coil has burned out.

Quick DIY Checks

1. 1Count the blink code precisely: stand in front of the furnace, open or look through the inspection window on the lower door panel, and count the number of LED flashes in one complete sequence (flash-flash-flash...pause...repeat). Write down the count — this is your fault code number. Some sequences look similar at 3 and 4 flashes, so count at least two full cycles to confirm.
2. 2For a 3-flash pressure switch code: locate the rubber pressure hose (typically 1/4 inch diameter tubing) that runs from the inducer housing or secondary heat exchanger to the pressure switch. Inspect the full length for kinks, cracks, or condensate blockage. Disconnect both ends and blow through the tube to verify it is clear. Reconnect and cycle the furnace. If the 3-flash persists, set a multimeter to continuity mode and test the pressure switch: disconnect the hose from the switch port and apply gentle suction with your mouth — the switch should click and beep continuity. No click or no beep means the switch has failed. On Goodman 90+ efficiency models, also check the secondary heat exchanger drain for blockage — a clogged drain traps condensate and reduces inducer suction.
3. 3For a 4-flash high limit code: replace the air filter immediately regardless of its appearance — a partially clogged filter can still cause high-limit trips. Check that all supply registers are open (at least 80% open across the home) and that the return air path is clear. After replacing the filter, let the furnace cool for 15–30 minutes and cycle it. If 4-flash returns with a fresh filter, the high-limit switch may have failed open and requires replacement, or the blower motor is not running at proper speed.

1. 4For a 6-flash ignition failure code: turn off the furnace at the power switch and gas valve. Locate the hot surface igniter — it sits in the burner assembly and is visible through the sight glass when it glows. Remove the igniter (one screw, then unplug the connector) and test resistance with a multimeter set to ohms. Silicon nitride igniters read 40–90 ohms. Silicon carbide igniters (older Goodman models) read 40–75 ohms. OL (open) means the igniter element has cracked and needs replacement. Inspect the igniter visually for hairline cracks — a cracked igniter may still measure resistance but fail to glow at full voltage.
2. 5For a 7-flash low flame signal code: turn off power and gas. Locate the flame sensor rod — a thin metal rod (approximately 3 inches long) mounted in the burner assembly with a ceramic insulator and a single wire connector. Remove the sensor (one screw) and lightly buff the metal rod with 120-grit emery cloth or fine steel wool to remove the white/gray oxide coating. Do not buff the ceramic insulator — only the metal rod tip. Reinstall, restore power, and run a heat cycle. The furnace should light and stay on. If the flame signal is still low after cleaning, check the wire connector at the board for corrosion, and verify the ground wire from the furnace chassis to the gas valve is secure.
3. 6Lockout reset procedure (applies to 2-flash and 6-flash lockout codes): turn the thermostat down or set it to OFF. Switch the furnace power switch (the wall switch near the unit) to OFF. Wait 30 seconds. Restore the power switch, then set the thermostat to HEAT at least 5°F above room temperature. The furnace should begin a normal startup sequence. If the board immediately re-enters lockout without attempting a full ignition cycle, the underlying fault was not corrected before the reset. Continue diagnosing the ignition system before resetting again. For Goodman models with a 24V control board, pressing and holding the rollout reset button (red button on the rollout switch, if present) may also be required after a rollout event.

Repair vs Replace

Recommended Tools & Parts

• Goodman Universal Hot Surface Igniter (Silicon Nitride)

  Replacement silicon nitride igniter for Goodman, Amana, and Daikin furnaces. Fixes 6-flash ignition failure lockout. Check your furnace model for 120V or 80V version. Part numbers B1401015S, 20164703, and B1401015 are common Goodman/Amana igniters.

  $25–$60

  Buy on Amazon →

• Goodman Flame Sensor Rod

  OEM-style replacement flame sensor rod for Goodman and Amana gas furnaces. Fixes 7-flash low flame signal after cleaning fails. Match connector style to your existing sensor.

  $15–$35

  Buy on Amazon →

• Goodman Draft Inducer Pressure Switch

  Replacement pressure switch for Goodman and Amana furnaces — fixes 3-flash pressure switch fault when hose is clear. Match the wye-number (water column rating) printed on your existing switch.

  $20–$55

  Buy on Amazon →

• Goodman High Limit Switch

  Replacement high-temperature limit switch for Goodman/Amana furnaces. Fixes 4-flash high limit code when filter and airflow have been verified. Match temperature rating (typically 140°F–200°F) and diameter to original.

  $15–$40

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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