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Goodman Furnace 4 flashes: Open primary or auxiliary limit

Updated October 2026 · Sourced from Goodman documentation

🧭 Check a few things first

A limit switch opened, so the circulator blower runs until it closes. The manual lists low airflow from a dirty filter or duct resistance, a faulty limit, a faulty blower or a blower speed set too low.

Is it safe to keep running? Check the steps below first. If it returns with a clean filter and open vents, call a licensed technician to check the limit switch, blower and speed setting.

4 flashes at a glance

Code / how it showsMeaningApplies to
4 flashes
Diagnostic LED seen through the blower door window
Open primary or auxiliary limitGoodman GMS8 / Amana AMS8 / GDS8 / ADSS8 80% single-stage gas furnaces (older flash-code control)

Check this first

Only steps a homeowner can do safely. Do not open electrical panels or the burner area.

  1. Replace the air filter if it is dirty, and make sure the supply and return vents are open and not blocked.
  2. Turn the furnace power off at the switch or breaker, wait one minute, then turn it back on to see whether the code returns.

🛑 Stop and call a licensed pro if

  • If it returns with a clean filter and open vents, call a licensed technician to check the limit switch, blower and speed setting.
  • You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
  • Flame rollout, limit or pressure switch codes that come back after one reset.
  • Anything involving the control board, gas valve, flame sensor, igniter or venting.
  • A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.

Safe first steps for any Goodman code

  1. Count the LED flashes through the blower door window before you switch anything off. Cutting power can clear the code.
  2. Replace or clean the furnace air filter.
  3. Check the thermostat: correct mode, set above room temperature, and fresh batteries.
  4. Make sure the furnace power switch and breaker are on. If the furnace has locked out, turning the power off and back on once restarts it.
  5. Make sure the gas valve is in the ON position, following the lighting instructions on the furnace label only.
  6. On high-efficiency furnaces, look at the outside vent and intake pipes for snow, ice, leaves or nests (look only, do not take pipes apart).

Source: Goodman GMS8/AMS8/GDS8/ADSS8 80% Single Stage Service Instructions RS6612006 (July 2013), pp.37-39. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.

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Related Goodman codes

1 flash : Ignition lockout (no flame)2 flashes : Pressure switch stuck closed3 flashes : Pressure switch stuck open5 flashes : Flame sensed with no call for heat6 flashes : Open rollout limit7 flashes : Low flame sense signal8 flashes : Igniter circuit fault or poor groundContinuous flash : Reversed polarity or poor ground (continuous or rapid flash)E0 : Lockout after three failed ignition attemptsE1 : Low-stage pressure switch closed at start of heatingE2 : Low-stage pressure switch circuit openE3 : Primary limit circuit open (furnace overheating)

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