Code: F04🔥 Goodman Gas Furnace

Goodman F04 Code: Blower Speed 4 Setting, Not a Fault (Meaning, What to Check)

Reviewed 2026-10-25 · Based on 2 manufacturer & service sources

What the code means

Goodman's service instructions for the GR9T96/GD9T96 two-stage furnace (also sold as Amana AR9T96/AD9T96) explain that when you open a blower speed menu, the display shows "the selected speed number as Fxx (xx: Blower speed number)," with speeds F01 through F09. Each mode has its own stored speed: FSd for continuous fan, AC1 and AC2 for first- and second-stage cooling, and gA1 and gA2 for low- and high-stage gas heat. In Goodman's speed tables, F04 is the default for low-stage cooling (Y or Y1 from the thermostat), one of three allowed speeds for low-stage heat (F01 default, F03, F04), and one of three for high-stage heat (F02 default, F04, F05). The same menus and tables appear in the service instructions for the Daikin DR96TN/DD96TN furnace. Real faults look different. Goodman lists Err as the active alarm menu and F10 as the last 10 faults menu, and both show codes as Exx. During normal running the display shows things like IdL (idle), 1AC or 2AC (first- or second-stage cooling). So a display showing 1AC together with F04 is describing first-stage cooling at blower speed 4. Note that a few third-party code lists call F04 a high-limit fault on Goodman furnaces; Goodman's own literature for these boards doesn't support that, and the limit fault on these furnaces is EE3.

Likely causes

Safe DIY checks

⚠ Before you start

Turn off power at the furnace/HVAC service switch and the breaker before opening panels. Shut the gas valve before any work near the burners, and never disconnect or alter the gas line. If you smell gas, leave the house and call your gas utility.

  1. Read the whole display sequence, not just F04. Write down any code that starts with E, plus mode words like IdL, 1AC or 2AC.
  2. If the display shows 1AC or 2AC and the indoor blower is running but the air isn't cold, the furnace is doing its part. Check that the outdoor unit is running and its breaker or disconnect is on.
  3. If the furnace won't heat, look for an E code. On these Goodman boards the Err menu shows the active alarm and F10 shows the last 10 faults.
  4. Replace a dirty air filter. It doesn't change F04, but restricted airflow is behind several real Goodman faults, including the EE3 limit code.
  5. Don't change blower speed settings just to make F04 go away. Speeds are set to match the cooling coil and the furnace's temperature rise, and the wrong speed can cause comfort or limit problems.

🛠 When to call a pro

  • The furnace shows an E code alongside or instead of F04. That code is the one to report when you book service.
  • The display shows a normal cooling call (1AC or 2AC) but the outdoor unit won't run or blows warm air.
  • You think the blower speed is set wrong, for example the system is noisy or the coil freezes. A technician should set the cooling and heating speeds using Goodman's airflow and temperature-rise tables for your model.
  • The system is under warranty. Call your Goodman, Amana or Daikin dealer.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Furnace air filter

Match the size printed on your current filter. Not an F04 fix, but basic airflow care for any furnace.

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⚙

Digital multimeter

For a technician or experienced DIYer checking 24-volt thermostat calls if the system really isn't working.

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Sources

  1. Goodman GR9T96/GD9T96 and Amana AR9T96/AD9T96 Two Stage Furnace Service and Troubleshooting (blower speeds shown as Fxx, F01 to F09; speed tables; Err, F10, FSd, AC1, AC2, gA1, gA2 menus; IdL and 1AC/2AC displays)
  2. Daikin DR96TN/DD96TN Two Stage Furnace Service Instructions (same Fxx blower speed menus and speed tables; Goodman-hosted)

Last reviewed 2026-10-25. Always confirm against the manual for your exact model number.