Why Goodman Furnace Lights Then Shuts Off: Troubleshooting and Repair Guide

The Goodman furnace that lights then shuts off is a common HVAC complaint that can stem from safety sensors, airflow issues, ignition faults, or venting problems. This guide explains likely causes, step-by-step troubleshooting, diagnostic tips for Goodman control boards, and repair or replacement options to help identify and resolve the issue safely.

Symptom	Common Cause	Quick Fix
Lights, then immediate shutdown	Ignition or flame sensing failure	Clean flame sensor, check ignition spark
Runs briefly, then shuts off after a minute	Pressure switch, vent blockage, or limit switch	Inspect venting, check pressure tubing, replace limit switch if bad
Cycles repeatedly	Thermostat wiring or control board error	Check thermostat settings and wiring, read LED error code

How Goodman Furnaces Control Ignition And Safety

Goodman furnaces use a sequence: the thermostat calls for heat, inducer motor runs, pressure switch verifies venting, ignition control energizes the gas valve or hot surface igniter, flame sensor confirms combustion, and the blower runs. If any safety device fails to confirm its step, the control board shuts the system down to prevent dangerous conditions.

Common Causes When Furnace Lights Then Shuts Off

1. Dirty Or Faulty Flame Sensor

The flame sensor detects flame presence; a thin layer of carbon or oxidation prevents a reliable signal. The board interprets this as no flame and closes the gas valve, causing the furnace to light briefly then shut off. Cleaning or replacing the sensor typically resolves the issue.

2. Ignition Or Hot Surface Igniter (HSI) Problems

If the HSI or spark ignition weakens, ignition may be intermittent. A partial or delayed flame can trigger a shutdown. Visual inspection of the igniter and electrical tests for resistance help determine if replacement is required.

3. Pressure Switch Or Inducer Motor Faults

The pressure switch confirms the inducer creates proper vent draft. Restricted venting, a clogged condensate trap, kinked pressure tubing, or a failing inducer motor can prevent the switch from closing. The furnace may light when the switch intermittently closes then shut off when the switch opens again.

4. Limit Switch Or Overheat Condition

A tripped high-limit switch indicates poor airflow or blocked return vents, causing the furnace to shut down after short runtime. Dirty filters, closed supply registers, or blower motor issues can create overheating and repeated shutdowns.

5. Gas Valve Or Gas Supply Problems

A defective gas valve or interrupted gas supply can cause flame instability. A failing valve may let gas flow briefly or inconsistently, or a utility supply issue may create pressure drops under load, triggering the safety shutdown sequence.

6. Control Board Or Diagnostic Error Codes

Goodman control boards provide LED blink codes or a digital display to signal faults. Intermittent electronic faults, poor solder joints, or failed relays can cause repeated light-then-shut cycles. Reading the LED flash pattern helps isolate the failure category.

How To Read Goodman Furnace LED Codes

Locate the control panel and find the status LED. Count flashes in the repeating sequence; most Goodman units use a long flash followed by short flashes indicating specific errors (e.g., pressure switch, flame sensed, high-limit). Consult the furnace data plate or Goodman manual for the exact code mapping.

Step-By-Step Troubleshooting Checklist

1. Verify thermostat settings and replace batteries to rule out user error.
2. Check HVAC filter and replace if dirty; restricted airflow causes shutdowns.
3. Watch the ignition sequence: does inducer run, then ignition occur, then immediate shutdown? Note timing.
4. Inspect return/supply vents and blower operation for airflow problems.
5. Locate and clean the flame sensor with emery cloth or fine sandpaper; do not over-sand.
6. Examine igniter for cracks or discoloration and test with multimeter per manufacturer resistance specs.
7. Inspect pressure switch tubing for water, cracks, or obstructions; blow through hose to confirm clearance.
8. Check condensate trap and drain for blockage on high-efficiency units; trapped condensate can affect pressure switches.
9. Read and record control board LED codes and refer to manual for diagnosis.
10. Listen for inducer motor starting failures or unusual noises indicating failing motor or bearings.

Testing And Safety Tips

Always turn power off at the breaker and shut the gas off before servicing internal components. Use a multimeter to test continuity on switches and resistance on igniters. Check for 24VAC from the transformer to the gas valve and ignition control. If uncomfortable with gas or electrical testing, contact a licensed HVAC technician.

Cleaning Or Replacing The Flame Sensor

Most flame sensors are easy to access and can be cleaned in minutes: power off, remove sensor, gently clean the metal rod, reassemble, and test. If cleaning fails, replace the sensor; replacement parts are inexpensive and often resolve flame-detection shutdowns.

When The Pressure Switch Is To Blame

Common pressure switch issues include blocked venting, clogged condensate lines, failed inducer motors, and collapsed tubing. Inspect all vent terminations outside for bird nests or debris, ensure exhaust piping slopes correctly, and confirm the inducer runs smoothly. Replace damaged tubing and test switch continuity while inducer runs.

Dealing With Limit Switch And Airflow Problems

Replace dirty filters, restore closed return registers, and inspect the blower wheel and motor for dust or obstruction. Test limits for continuity; a limit that trips prematurely may need replacement but check underlying airflow causes first to prevent repeat failures.

Control Board And Gas Valve Concerns

If LED codes point to control board faults or if voltage to the gas valve is inconsistent, inspect wiring connections and caps for corrosion. A failing control board may show intermittent relay activation or burn marks. Gas valves that respond inconsistently to a steady 24VAC signal should be replaced by a trained technician due to gas safety requirements.

Estimating Repair Costs

Common repairs and typical U.S. cost ranges (parts and labor):

Repair	Estimated Cost
Flame Sensor Cleaning/Replacement	$80–$200
Igniter Replacement	$150–$400
Pressure Switch Or Tubing Repair	$120–$350
Inducer Motor Replacement	$250–$600
Control Board Replacement	$300–$900
Gas Valve Replacement	$300–$800

Prices vary by region, unit model, and whether the unit is under warranty. Always request written estimates and check technician licensing and insurance.

When To Call A Professional

• If the furnace has a gas odor or suspected leak, evacuate and call the gas company and a licensed technician immediately.
• If LED codes indicate control board, gas valve, or inducer motor failure that requires component replacement.
• If electrical testing is beyond the homeowner’s comfort level or if safety controls repeatedly trip after attempted fixes.

Preventive Maintenance To Avoid Future Shutdowns

Schedule annual professional tune-ups, replace filters every 1–3 months, keep combustion air and vent terminations clear, and clean the flame sensor during routine service. Regular checks reduce the chance of intermittent failures and improve efficiency.

Model-Specific Notes For Goodman Units

Goodman furnaces often use a diagnostic LED or control board sticker with code meanings; newer models may include digital displays. Maintain the unit’s serial/model number when ordering parts and consult Goodman’s technical documents or authorized dealers for OEM guidance.

Quick Troubleshooting Flowchart (Summary)

1. Thermostat Check → Replace batteries, confirm mode and setpoint.
2. Airflow Check → Replace filter; ensure vents open; verify blower operation.
3. Ignition Sequence → Observe inducer, ignition, flame, and shutdown order.
4. Flame Sensor → Clean or replace if flame is present but not detected.
5. Pressure/Venting → Inspect tubing, condensate, and outdoor vent termination.
6. Control Board Codes → Read LED flashes and follow code-specific repair steps.

Additional Resources And Documentation

For model-specific diagrams and LED code tables, consult the Goodman furnace installation and service manual or the Goodman website. Many authorized HVAC forums and manufacturer PDFs provide wiring diagrams and component locations to assist qualified technicians.

Key Takeaways

Repeated light-then-shut behavior commonly indicates flame sensing, pressure switch, airflow, or control board issues. Homeowners can perform basic checks like filter replacement and flame sensor cleaning, but gas, electrical, and control board repairs are best handled by licensed HVAC professionals to maintain safety and warranty compliance.

If persistent problems remain after basic troubleshooting, contact a certified Goodman technician, provide LED error codes, and document observed behaviors to streamline diagnosis and repair.