Updated 2026-06-25
Goodman Furnace 4 flashes: What It Means & How to Fix It
Compiled & reviewed by Nikolai Tsyrenov · Updated 2026-06-25 · confidence: high
What does Goodman furnace 4 flashes mean?
Primary limit circuit (high-limit switch) is open — usually from restricted airflow. Most often caused by Restricted airflow from a dirty/clogged air filter (most common).
What Goodman furnace 4 flashes means
Primary limit circuit (high-limit switch) is open — usually from restricted airflow.
Common causes
- Restricted airflow from a dirty/clogged air filter (most common)
- Restrictive ductwork, closed or blocked registers/returns
- Improper circulator blower speed or a failing blower motor
- Loose or improperly connected wiring in the high-limit circuit
Homeowner-safe steps to try
- Turn the thermostat OFF and check/replace the air filter
- Open all supply registers and clear return-air grilles of obstructions
- Remove rugs, furniture, or boxes blocking airflow
- Cycle power at the furnace switch after correcting airflow; do NOT bypass the limit switch
When to call a licensed HVAC technician
If the basic checks below don't clear the code, the fault recurs, or anything involves the gas valve, burners, flame sensor or wiring, stop and book a licensed HVAC technician. Repairs to the combustion or gas system are not DIY.
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
When to call a pro: Call a licensed HVAC technician if 4 flashes return after replacing the filter and clearing vents — a repeatedly open limit can indicate a blower or duct problem and risks overheating.
Goodman furnace 4 flashes FAQ
What does Goodman furnace 4 flashes mean?
Primary limit circuit (high-limit switch) is open — usually from restricted airflow.
What causes Goodman furnace 4 flashes?
Common causes: Restricted airflow from a dirty/clogged air filter (most common); Restrictive ductwork, closed or blocked registers/returns; Improper circulator blower speed or a failing blower motor; Loose or improperly connected wiring in the high-limit circuit.
Can I fix Goodman furnace 4 flashes myself?
You can safely try: Turn the thermostat OFF and check/replace the air filter; Open all supply registers and clear return-air grilles of obstructions; Remove rugs, furniture, or boxes blocking airflow; Cycle power at the furnace switch after correcting airflow; do NOT bypass the limit switch. Call a licensed HVAC technician if 4 flashes return after replacing the filter and clearing vents — a repeatedly open limit can indicate a blower or duct problem and risks overheating.
Other Goodman furnace codes
Goodman 1 flashLockout due to too many ignition retries (3) —Goodman 2 flashesPressure-switch circuit is stuck closed at theGoodman 3 flashesPressure-switch circuit is open (did not closeGoodman 5 flashesFlame sensed with no call for heat — the contrGoodman 6 flashesFlame-rollout switch is open — a safety shutdoGoodman 7 flashesLow flame signal — the flame-sense micro-amp sGoodman 8 flashesProblem with the igniter circuit.
Sources: hvacdirect.com · inspectapedia.com. General information for homeowners, not professional advice — confirm against your furnace's manual and a licensed technician.