The article explains common causes, diagnostic steps, and solutions when an Armstrong Air furnace is not igniting. It covers safety checks, electronic ignition systems, pilot light issues, control board faults, and when to call a professional. The goal is to help homeowners identify likely problems and decide next steps safely and efficiently.
| Symptom | Likely Cause | Quick Action |
|---|---|---|
| No ignition and no blower | Thermostat, power, or faulted control board | Check thermostat and breaker, reset power |
| Clicking but no flame | Ignitor or gas supply issue | Inspect ignitor and gas valve, call tech if needed |
| Pilot lights then goes out | Thermocouple or flame sensor problem | Clean sensor, replace if needed |
| Intermittent ignition | Loose wiring or failing control module | Secure connections, monitor cycles |
How Armstrong Air Furnaces Ignite: Basic System Overview
Armstrong Air furnaces typically use standing pilot or electronic ignition systems. Modern units almost always use an electronic hot surface ignitor (HSI) or intermittent pilot with a flame sensor. The thermostat signals the furnace control board, which sequences safety checks, opens the gas valve, and activates the ignitor. A flame sensor or thermocouple confirms ignition, allowing the furnace to run the blower on its heat cycle.
Initial Safety And Power Checks
Before diagnosing ignition, ensure safety. Turn off power at the furnace switch and the circuit breaker for any wiring work. Verify the gas supply is on and there is no gas odor. If gas smell exists, evacuate and call the gas company immediately.
Check the thermostat settings and batteries. Confirm the furnace switch is on and the unit has power at the breaker. A tripped breaker, blown fuse, or a switched-off disconnect will prevent ignition.
Thermostat And Control Board Communication
A common non-ignition cause is lack of signal from the thermostat. Replace thermostat batteries and verify that the thermostat is set to heat with a target temperature above room temperature.
Measure for a 24VAC call for heat at the furnace control board terminals labeled R and W. No 24VAC indicates a thermostat or wiring issue. If present, the board should proceed to the ignition sequence. If the board receives a call but does nothing, the control board may be faulty.
Ignition System Types And Failures
Identify the ignition type: hot surface ignitor (HSI), intermittent spark, or standing pilot.
Hot Surface Ignitor (HSI)
HSIs glow red-hot to ignite gas. They are fragile and can crack or burn out. If the furnace clicks or the gas valve opens but no flame appears, the ignitor is a likely suspect. Visual cracks or a non-glowing element indicate replacement is needed.
Intermittent Pilot And Spark Ignitors
Spark systems produce a spark to light the pilot or main burner. Weak or absent sparks point to a failed transformer, ignition module, or grounding problem. Visual inspection for damaged electrodes and checking spark gap and wiring help diagnose the issue.
Standing Pilot And Thermocouple
Older Armstrong units may use a standing pilot with a thermocouple. A weak pilot flame or a failed thermocouple prevents the gas valve from staying open. Cleaning the pilot or replacing the thermocouple often restores operation.
Flame Sensor And Thermocouple Issues
The flame sensor detects the burner flame and tells the control board to keep the gas valve open. A fouled or corroded flame sensor will cause the furnace to shut off the gas shortly after ignition. Cleaning the sensor with fine steel wool or emery cloth often fixes the problem.
If cleaning fails, test the thermocouple or sensor for proper millivolt output per the manufacturer specifications. Replace the flame sensor or thermocouple if it reads out of range.
Gas Supply Problems
Gas pressure and the gas valve condition are crucial. If the furnace tries to ignite but no gas is present, the ignition will fail. Confirm the home’s gas supply is active and other gas appliances operate normally.
Inspect the furnace’s gas valve for obvious signs of damage. A multimeter can test the solenoid coils to ensure the valve is being energized when the control board commands it. A faulty gas valve requires professional replacement because it involves gas piping and safety protocols.
Draft, Venting, And Pressure Switches
Condensing Armstrong furnaces use induced draft blowers and pressure switches. If the inducer motor fails or the pressure switch does not close, the furnace will not allow ignition. Listen for the inducer starting when the furnace calls for heat. If the inducer does not run, inspect power, capacitor, and motor connections.
Check pressure tubing for blockages and verify the pressure switch continuity when the inducer is running. Replace a stuck or faulty pressure switch if it fails to close during start-up.
Common Error Codes And Diagnostics
Armstrong furnaces often use LED status codes on the control board. Refer to the data plate or manual for code meanings. Common codes include ignition lockout, flame failure, and pressure switch faults.
Count LED flashes to identify the error. For example, repeated two-flash codes may indicate limit switch tripping or pilot failure. Use the board code table to pinpoint the subsystem requiring attention.
Step-By-Step Troubleshooting Checklist
- Confirm thermostat is calling for heat and set correctly.
- Verify furnace power: switch on, breaker not tripped, fuse intact.
- Check gas supply to the home and furnace gas shutoff valve position.
- Listen for inducer motor and ignition attempts; note any clicking or spark sounds.
- Inspect ignitor visually; replace if cracked or non-glowing.
- Clean flame sensor or thermocouple and retest ignition cycle.
- Check pressure switch tubing and inducer operation for venting issues.
- Read control board LED error codes and consult manual for specifics.
- Test voltage to gas valve and continuity of safety switches with a multimeter.
- If the issue persists or involves gas valve replacement, call a licensed HVAC technician.
When To Replace Parts Versus Repair
Ignitors, flame sensors, and filters are relatively low-cost parts often replaced during routine service. Replace an ignitor when it visibly cracks or fails resistance tests. Replace a flame sensor if cleaning does not restore reliable sensing.
A control board or gas valve replacement is more expensive and requires professional diagnosis. Consider replacement when repeated component replacements do not solve the problem, when the board shows multiple faults, or when safety devices fail intermittently.
Maintenance Tips To Prevent Ignition Failures
Regular maintenance reduces ignition problems. Replace air filters every 1–3 months to avoid reduced airflow and limit trips. Schedule annual furnace tune-ups with a licensed HVAC technician to clean burners, inspect the flame sensor, and test ignition components.
Keep the area around the furnace clean to prevent debris from entering the combustion chamber. Ensure proper venting and clear any bird nests or blockages from the exhaust system on outdoor vents.
DIY Safety And Tools Needed
Basic homeowners’ troubleshooting needs a few tools: a screwdriver set, multimeter, flashlight, fine abrasive pad for cleaning sensors, and a replacement ignitor or flame sensor if identified as faulty. Always shut power and gas before accessing internal components.
Never attempt gas valve replacement or complex control board work without proper training. Improper handling can produce gas leaks, fires, or carbon monoxide hazards. When in doubt, contact a certified HVAC technician.
When To Call A Professional
Call a professional if there is a gas odor, if the gas valve or control board is suspected, when pressure switches or inducer motors are involved, or if the homeowner lacks the tools or comfort to safely test electrical components.
A qualified technician performs safe gas valve changes, pressure tests, and diagnostic checks with industry-grade tools and follows code requirements. Request proof of licensing and insurance for liability protection.
Cost Estimates And Warranty Considerations
Typical replacement costs: ignitor $50–150, flame sensor $30–80, pressure switch $50–150, control board $200–600, gas valve $300–800 plus labor. Prices vary widely by region and model complexity.
Check the furnace warranty and any extended service plans. Many Armstrong Air parts are covered under manufacturer warranties for a specified period. Retain service records and serial numbers when scheduling repairs.
Additional Resources And Documentation
Consult the furnace data plate and owner’s manual for model-specific wiring diagrams and LED code charts. Manufacturer websites often provide downloadable manuals and troubleshooting guides.
For safety information about gas and carbon monoxide, reference the U.S. Consumer Product Safety Commission (CPSC) and the National Fire Protection Association (NFPA) recommendations. Local utility companies can assist with suspected gas supply problems.
Key Takeaways For Homeowners
- Start simple: check thermostat, power, and gas supply first.
- Common culprits: ignitor, flame sensor, pressure switch, and gas valve.
- Clean before replace: flame sensors often respond to cleaning.
- Safety first: evacuate for gas smells and hire pros for gas-valve or control-board work.
- Preventive maintenance: annual service and filter changes reduce ignition failures.
If troubleshooting does not restore ignition, document observed behaviors and LED codes before calling an HVAC technician to speed diagnosis and reduce repair costs.