The Goodman furnace ignitor glows but no flame appears when ignition sequence fails. This article explains common causes, step-by-step troubleshooting, safety checks, and when to call a professional. It helps readers diagnose why the ignitor glows without producing a flame and how to resolve the issue safely and cost-effectively.
| Symptom | Likely Causes | Suggested Action |
|---|---|---|
| Ignitor Glows But No Flame | Gas valve issue, flame sensor, pressure switch, ignition control board, closed gas supply | Check gas supply, test flame sensor, inspect gas valve and control board, call HVAC tech |
| Clicking Or Repeated Tries | Weak ignitor, failed control cycle, blocked vent | Replace ignitor, clear venting, examine control board |
| Intermittent Operation | Loose wiring, failing gas valve, thermostat fault | Tighten connections, test valve, verify thermostat |
How A Goodman Furnace Ignitor Works
The Goodman furnace ignitor is an electronic device that heats until it reaches a temperature that will ignite the gas. When the thermostat calls for heat, the sequence begins: the inducer motor runs, pressure switches confirm proper venting, the ignitor glows, the gas valve opens, and the flame sensor confirms ignition. If the ignitor glows but no flame appears, the sequence breaks downstream of the ignitor.
Common Causes When The Ignitor Glows But No Flame
1. Gas Supply Or Shutoff Issues
A closed gas valve, turned-off gas supply, or a blocked gas line prevents gas from reaching the burners even though the ignitor glows. Users should confirm that the home’s gas supply and the furnace’s gas shutoff are open.
2. Faulty Gas Valve
The gas valve controls flow to the burners and is activated by the furnace control board. A mechanically or electrically failing gas valve may not open, causing no flame even with a glowing ignitor.
3. Malfunctioning Flame Sensor
The flame sensor detects flame presence and signals the control board. A dirty or failing flame sensor may fail to detect the flame, causing the system to shut off the gas or prevent ignition in subsequent cycles.
4. Control Board Or Ignition Sequencer Failures
If the control board fails to send the signal to the gas valve, the ignitor will glow but no gas will be released. Control board faults or a failing ignition module are common causes when wiring and gas supply are correct.
5. Pressure Switch Or Venting Problems
If the inducer motor and pressure switches do not confirm proper venting, the furnace will not open the gas valve. A clogged vent, blocked exhaust, or faulty pressure switch can interrupt the startup sequence even after the ignitor glows.
6. Thermostat Or Wiring Issues
A thermostat that sends intermittent or incorrect signals or loose wiring between components can prevent the ignition cycle from completing. The ignitor may still glow while the gas valve receives no command.
Safety First: Precautions Before Troubleshooting
Turn off power to the furnace at the breaker and close the gas supply for safety. If a gas odor is present, evacuate the area and call the gas utility or emergency services. Working with gas and high-voltage components can be hazardous; when in doubt, contact a licensed HVAC technician.
Step-By-Step Troubleshooting Guide
Visual And Basic Checks
Start with quick checks: confirm the thermostat calls for heat, the furnace power switch is on, and the gas shutoff valve is open. Look for error codes on the Goodman furnace control board LED or the thermostat. Note the sequence: inducer motor, ignitor glow, then gas valve operation. This pattern helps isolate the failure stage.
Check For Gas Supply
Verify gas is available to the home and the furnace. If other gas appliances work, the issue is likely inside the furnace. If no gas is available, contact the gas company.
Listen And Observe The Sequence
When the thermostat calls for heat, listen for the inducer motor and the sound of the gas valve opening. If the ignitor glows but there is no gas clicking or whoosh of ignition, the gas valve or control signal may be at fault.
Inspect And Clean The Flame Sensor
A dirty flame sensor often prevents flame verification. Remove the flame sensor and clean it gently with fine-grit sandpaper or steel wool. Reinstall and test. Cleaning the flame sensor is a common, low-cost fix for ignition detection issues.
Test The Gas Valve
Testing the gas valve requires multimeter skills and knowledge of millivolt signals. Measure the voltage to the gas valve during a call for heat; a lack of voltage indicates a control board or wiring problem. If voltage is present but the valve doesn’t open, the gas valve likely needs replacement.
Check Pressure Switch And Venting
Inspect the vent and intake for blockages from debris, nests, or ice. Test the pressure switch tubing for cracks or disconnections. A faulty pressure switch or blocked vent will prevent the gas valve from opening even when the ignitor glows.
Evaluate The Control Board And Ignition Module
Look for error codes or burned components on the control board. Inspect wiring connectors for corrosion or loose connections. Replacement of the board or ignition module is sometimes necessary when diagnostics show control failures.
Examine Thermostat And Wiring
Confirm thermostat settings and battery condition. Check the 24V wiring between the thermostat and furnace. Replace or bypass the thermostat to test whether the control board responds correctly to a call for heat.
When To Call A Professional HVAC Technician
Call a licensed technician when troubleshooting requires gas valve replacement, control board repair, complex electrical diagnosis, or when a gas leak is suspected. HVAC professionals have specialized tools, access to replacement parts, and can safely handle gas system repairs and code compliance.
Typical Repair Costs And Timeframes
Costs vary by region and severity. Common estimates: flame sensor cleaning or replacement $75–$150; ignitor replacement $100–$300; gas valve replacement $300–$700; control board replacement $200–$800. Labor and parts can increase total costs, and diagnostics typically take 1–2 hours.
Replacement And Parts Considerations
Use OEM or manufacturer-recommended parts for Goodman furnaces to ensure compatibility and maintain warranties. Record model and serial numbers before ordering parts. Consider professional installation for gas valve and control board replacements to ensure proper calibration and safety checks.
Preventive Maintenance To Avoid Future Failures
- Schedule annual professional furnace tune-ups including burner and flame sensor cleaning.
- Replace air filters regularly to reduce dust buildup that can affect combustion components.
- Keep vents and chimneys clear of debris and perform seasonal inspections for animal nests.
- Verify proper thermostat function and wiring integrity during routine maintenance.
- Install carbon monoxide detectors and test them regularly to detect combustion issues early.
Common Diagnostic Checklist For Technicians
- Confirm thermostat call for heat and observe ignition sequence.
- Check for gas supply and open shutoff valve.
- Inspect inducer motor operation and pressure switch continuity.
- Verify ignitor glows and measure its resistance or current draw.
- Check gas valve voltage during ignition attempt.
- Clean or test flame sensor for millivolt signal when flame is present.
- Evaluate control board for error codes, burned components, and output signals.
- Test safety switches, limit switches, and venting integrity.
Troubleshooting Tips Specific To Goodman Furnaces
Goodman units often display diagnostic LED flash codes on the control board. Consult the furnace manual for code meanings. Document flash patterns and provide them to the technician to speed diagnosis. Replace parts with compatible Goodman or OEM-rated components to preserve system reliability.
When The Ignitor Fails Intermittently
Intermittent glowing often indicates a weak ignitor nearing end of life, failing control board outputs, or loose electrical connections. Replace aged ignitors proactively; they are fragile and degrade over time. Tighten and secure wiring and connectors during inspection.
Addressing Odors Or Safety Concerns
A rotten-egg smell indicates a gas leak. Evacuate immediately, avoid using electrical switches or phones inside, and call the gas company or emergency services. For persistent combustion odors during operation, stop the furnace and call a technician to inspect burners and venting.
Key Takeaways And Action Plan
If the Goodman furnace ignitor glows but no flame appears, focus on gas supply, gas valve operation, flame sensor condition, pressure switches, and the control board. Start with basic safety checks and simple fixes like cleaning the flame sensor. For gas valve or control board faults, contact a licensed HVAC technician. Timely diagnosis and preventive maintenance reduce repair costs and ensure safe furnace operation.
Resources And Further Reading
Consult the furnace manual for model-specific guidance, Goodman technical bulletins for known issues, and local code requirements for gas appliance repairs. For persistent or unsafe conditions, use a licensed HVAC contractor with Goodman experience.