Goodman Furnace Won’t Stay Lit: Troubleshooting and Repairs

A Goodman furnace that won’t stay lit can cause cold rooms, higher energy bills, and safety concerns. This article explains common causes, diagnostic steps, and practical fixes to restore reliable heating. It focuses on safe troubleshooting, when to call a professional, and ways to prevent recurrence.

Symptom	Likely Causes	Suggested Action
Ignites Then Goes Out	Pilot/ignition failure, flame sensor, gas valve	Clean sensor, test gas supply, inspect ignition module
Lights Flicker Or Intermittent	Thermostat, airflow issues, control board	Check thermostat settings, replace filters, inspect wiring
Smells Or Soot	Incomplete combustion, blocked venting	Turn off unit; call HVAC technician

How Goodman Furnaces Ignite And Why Flame Loss Happens

Goodman furnaces use either a standing pilot, hot surface ignitor (HSI), or intermittent pilot/Ignition Control to light the burners. The control system ensures the burner stays lit by detecting a proper flame signal and maintaining gas flow. When the furnace fails to stay lit, it means the flame detection or gas control sequence interrupted after ignition.

Common failure points include the flame sensor or ignitor, gas valve or pressure issues, blocked venting, dirty burners, thermostat or control board faults, and airflow problems that cause overheating and automatic shutdown.

Safety First: When To Stop Troubleshooting

If there is a strong gas smell, visible soot, persistent yellow flames, or frequent flameouts after attempts to relight, the furnace should be turned off and a qualified HVAC technician contacted. Natural gas leaks and carbon monoxide risk require immediate professional attention.

Tools And Basic Preparations For Troubleshooting

For safe and effective troubleshooting, a few basic tools are helpful: a multimeter, small screwdriver set, soft brush, fine-grit sandpaper or emery cloth, nut driver, flashlight, and a vacuum for dust removal. Turn off power and gas supply before accessing internal components unless the procedure explicitly requires powered checks.

Step-By-Step Diagnostics And Fixes

1. Verify Thermostat And Power

First confirm the thermostat is set to heat, the temperature is above the current room temp, and the fan setting is correct. Check circuit breakers and the furnace’s power switch. A tripped breaker or switched-off furnace will prevent continuous operation.

2. Inspect Airflow And Limit Switches

Restricted airflow from a clogged filter or blocked return vents can cause the furnace to overheat and trip the high-limit switch, shutting the burners off. Replace dirty filters, ensure vents are open, and inspect blower operation. If the furnace cools and restarts repeatedly, a faulty limit switch or overheating problem could be the root cause.

3. Check The Ignitor Or Pilot Assembly

For hot surface ignition systems, a cracked or weak HSI will ignite intermittently. Visual inspection often reveals cracks. Use a multimeter to test for continuity per manufacturer specs. For pilot-equipped units, ensure the pilot flame is steady and properly positioned. Replace a failing HSI or fix a misadjusted pilot flame.

4. Clean Or Replace The Flame Sensor

The flame sensor detects the presence of flame and tells the control board to keep the gas valve open. A dirty sensor often causes the furnace to ignite then shut down after a few seconds. Remove the sensor, gently clean it with fine-grit sandpaper or emery cloth, and reinstall. If cleaning does not help, replace the sensor with an OEM or compatible part.

5. Evaluate The Gas Supply And Gas Valve

Insufficient gas pressure or a failing gas valve can cause the burner to extinguish. If other gas appliances work, the supply is likely okay, but a partial blockage, regulator issue, or valve malfunction can still affect the furnace. A qualified technician should test gas pressure and diagnose gas valve operation due to safety and code requirements.

6. Check Burners And Venting

Dirty or misaligned burners can produce poor combustion and unstable flames. Inspect burners for rust, debris, or soot, and clean using a soft brush and vacuum. Ensure the venting and flue are clear of obstructions; blocked flues cause combustion products to back up and disrupt flame sensing and safety switches.

7. Inspect The Flame Rollout And Vent Safety Switches

Rollout switches detect flame escaping the combustion chamber. A triggered rollout switch cuts gas flow to the burners. If the furnace initially lights but the rollout switch trips, inspect for blocked heat exchanger passages, cracked heat exchanger, or vent issues. Replace tripped switches only after addressing the underlying cause.

8. Examine Control Board, Wiring, And Sensors

Loose connections, corroded terminals, or a failing control board can interrupt the ignition-holding sequence. Visually inspect wiring harnesses, connectors, and ground connections. Use a multimeter to verify 24V signals from the thermostat and continuity on safety switches. Replace a damaged control board if diagnostics indicate malfunction.

Common Error Codes And What They Mean

Many Goodman furnaces flash LED codes on the control board to indicate faults. Three flashes might indicate a flame sense failure, while five flashes can show pressure switch issues. Consult the furnace’s technical manual for exact code meanings. Recording and referencing these codes speeds diagnosis and reduces unnecessary parts replacement.

When Replacements Are Likely Needed

Parts commonly replaced when a Goodman furnace won’t stay lit include the flame sensor, hot surface ignitor, gas valve, pressure switch, and control board. Choose genuine Goodman or compatible OEM parts for reliability. Replace components after confirming through testing that the part is faulty.

Preventive Maintenance To Keep The Furnace Lit

Routine maintenance reduces the chance of flame loss. Recommended annual or biannual tasks include replacing filters every 1–3 months, cleaning burners and flame sensor, inspecting and testing safety switches, checking venting for obstructions, and having a licensed technician perform combustion analysis and heat exchanger inspection.

DIY Troubleshooting Checklist

• Confirm thermostat and power supply to the furnace.
• Replace dirty air filters and ensure vents are open.
• Visually inspect the ignitor and flame sensor; clean or replace as needed.
• Check burners for debris and clean them carefully.
• Inspect wiring for loose connections or corrosion.
• Record any control board LED error codes and consult manual.
• Smell for gas; if present, turn off gas and call the gas company or HVAC technician.

When To Call A Professional HVAC Technician

Professional service is recommended for gas pressure testing, internal gas valve replacement, heat exchanger inspection, vent system repair, and when safety devices repeatedly trip. A licensed technician can perform combustion efficiency and carbon monoxide tests to ensure safe operation.

Costs And Timeframe For Repairs

Repair costs vary by part and labor regionally. Typical ranges: flame sensor replacement $75–$200, hot surface ignitor $150–$400, gas valve $300–$800, control board $200–$600. Diagnostic fees may apply. Simple sensor cleaning or filter replacement can restore operation in under an hour, while major component replacement often takes a few hours including system testing.

Preventing Future Issues And Extending Furnace Life

Consistent maintenance extends furnace life and prevents flame loss. Schedule annual professional tune-ups, maintain clear airflow, install carbon monoxide detectors, and address unusual noises, smells, or performance drops immediately. Keep vent terminations clear of debris and landscaping growth.

Useful Resources And Manufacturer Support

Goodman provides manuals and technical bulletins that include wiring diagrams, error code definitions, and part numbers. OEM part catalogs and HVAC professional forums offer troubleshooting tips. For safety-related concerns or complex diagnostics, contact a licensed HVAC pro or Goodman technical support.

Key Takeaways

Frequent causes of a Goodman furnace not staying lit include dirty flame sensors, failing ignitors, gas supply issues, blocked venting, and safety switch trips. Start with safe, low-cost checks like filters and sensor cleaning, then escalate to professional service for gas and combustion system diagnostics. Prompt action preserves safety and prevents costly damage.