Armstrong Air Furnace Not Igniting: Troubleshooting and Fixes

The article explains common causes and practical fixes when an Armstrong Air furnace is not igniting, helping homeowners diagnose issues safely and determine when professional service is needed. It covers safety checks, common parts, step-by-step troubleshooting, and maintenance tips to restore reliable heating.

Symptom	Likely Causes	Quick Fix
No ignition or spark	Thermostat, pilot/ignitor, power	Check thermostat, reset power, inspect ignitor
Clicking but no flame	Gas valve, gas supply, pressure	Verify gas on, test valve, call tech
Short cycles	Limit switch, flame sensor, airflow	Clean sensors, change filter

How Armstrong Air Furnaces Ignite: Basic Principles

Armstrong Air furnaces use either a hot-surface ignitor or electronic spark and a gas valve to light the burners controlled by a thermostat and a control board. The ignition sequence normally powers the inducer motor, proves pressure switches, energizes the ignitor or spark module, opens the gas valve, and senses flame with a flame sensor or thermocouple.

Understanding this sequence helps isolate where ignition fails: electrical supply, control board signals, ignition device, gas delivery, or flame detection. Each step can be tested for continuity, voltage, or physical signs of wear.

Safety First: Precautions Before Troubleshooting

Always turn off power to the furnace at the switch near the unit and shut off the gas at the main valve before inspecting internal parts. Work in a well-ventilated area and evacuate if the smell of gas is present, then call the gas company or emergency services.

Use insulated tools and avoid touching hot components like heat exchangers. If the homeowner is uncomfortable with electrical or gas systems, contacting a licensed HVAC technician is the safest option.

Initial Checks: Quick Tests Homeowners Can Do

Start with simple checks: ensure the thermostat is set to heat and temperature is above room temperature, verify circuit breakers and furnace switch are on, and replace or inspect batteries in the thermostat. These steps fix many non-ignition issues quickly.

Confirm the gas supply is turned on at the house meter or appliance shutoff. If other gas appliances work but the furnace does not, the problem is likely internal to the furnace system rather than the supply.

Thermostat And Power Problems

If the furnace does not respond when the thermostat calls for heat, the thermostat, wiring, or control board may be at fault. Test by setting the thermostat to heat and raising the setpoint while listening for the furnace to start the inducer motor or hear clicking.

To check wiring, turn power off and inspect the R and W terminals for loose or corroded connections. Use a multimeter to check for 24V between R and W when the thermostat calls for heat; absence of 24V indicates thermostat or wiring issues.

Inducer Motor, Pressure Switch, And Venting Issues

If the inducer motor does not run or runs and then stops, the pressure switch or vent blockage may be preventing ignition. Condensing Armstrong furnaces rely on the inducer to clear combustion gases and close pressure switches before ignition.

Check for blocked vents or bird nests at the exhaust or intake. Listen for unusual inducer noise and use a multimeter to test the pressure switch for continuity when the inducer is running. A failed inducer or pressure switch requires repair or replacement.

Ignitor Problems: Hot-Surface Ignitor And Spark Systems

Hot-surface ignitors (ceramic elements) glow orange when working and are fragile. A cracked or broken ignitor will not light the burners. Spark ignition modules produce visible sparks at the electrodes.

Inspect the ignitor visually for cracks or discoloration and test for continuity with a multimeter if accessible. Replace hot-surface ignitors at the first sign of hairline cracks or if continuity is absent. Avoid touching the element with bare hands; oils shorten its life.

Gas Valve And Gas Supply Troubleshooting

If the ignitor works but no flame appears, the gas valve or gas supply is suspect. Confirm that the gas shutoff at the furnace is open and the home’s gas is flowing. If other gas appliances function, the internal gas valve or pressure regulator may be faulty.

Testing the gas valve requires measuring coil voltage with a multimeter as the thermostat calls for heat; a 24V signal should open the valve. If the valve receives voltage but does not open, it must be serviced or replaced by a qualified technician.

Flame Sensing And False Shutdowns

Some Armstrong units use a flame sensor or thermocouple to confirm ignition. A dirty or misaligned flame sensor can cause the control board to shut off the gas soon after ignition, creating cycling or failure-to-ignite conditions.

Clean the flame sensor gently with fine emery cloth or steel wool and ensure it is positioned within the flame envelope. If cleaning does not restore function, test the sensor with a multimeter or replace it.

Limit Switches, Rollout Switches, And Safety Interlocks

Limit switches and rollout switches protect against overheating or flame rollout. If one of these safety switches is open, the furnace will not ignite. These switches often trip due to airflow restrictions, blocked return vents, or a dirty heat exchanger.

Inspect air filters and return vents, replace clogged filters, and clear obstructions. Reset tripped switches only after addressing the underlying cause; repeated trips indicate a serious problem requiring professional diagnosis.

Control Board Diagnostics And Error Codes

Modern Armstrong furnaces have control boards with LED diagnostic lights that flash error codes. Consult the furnace manual or the label inside the access panel to interpret code patterns indicating issues like pressure switch failure, ignition failure, or blocked venting.

Use the control board diagnostics to narrow troubleshooting rather than replacing parts blindly. If codes indicate intermittent faults, record frequency and conditions to help a technician diagnose intermittent wiring or sensor failures.

Common Replacement Parts And Costs

Typical parts associated with ignition issues include the ignitor, flame sensor, gas valve, pressure switch, inducer motor, control board, and thermostat. Prices vary by model and region; approximate ranges are ignitor $40–$150, flame sensor $20–$80, gas valve $150–$450, inducer motor $150–$500, and control board $200–$800.

Labor costs for furnace repairs vary widely; expect higher rates during peak winter demand or in metropolitan areas. Obtain multiple estimates for major repairs and ensure warranties for parts and labor when available.

Maintenance Tips To Prevent Ignition Failures

Regular maintenance reduces ignition failures. Replace furnace filters every 1–3 months, keep vents and registers clear, schedule annual professional tune-ups, and ensure proper combustion airflow by cleaning burners and checking venting.

Additionally, inspect the furnace area for corrosion, rodent damage to wiring, or signs of moisture in condensing units. Early detection of these issues prevents ignition and safety problems.

When To Call A Professional HVAC Technician

If troubleshooting reveals gas valve failure, cracked heat exchanger, persistent safety switch trips, control board faults, or if the homeowner detects a strong gas smell, contact a licensed HVAC technician. These conditions involve safety risks and require specialized tools and certifications.

Choose a technician with Armstrong Air training or factory authorization when possible. Ask for written estimates, references, and proof of licensing and insurance prior to major repairs.

DIY Troubleshooting Checklist

• Verify thermostat settings and power at the breaker and furnace switch.
• Replace thermostat batteries and check wiring at R and W terminals for 24V during a call for heat.
• Inspect and replace clogged air filters to prevent limit switch trips.
• Listen to the inducer and check for vent blockages; clear debris from intake and exhaust.
• Visually inspect the ignitor for cracks; test continuity if comfortable using a multimeter.
• Clean the flame sensor with fine emery cloth if the furnace lights then shuts off.
• Confirm the gas shutoff valve at the furnace is open and other gas appliances operate.
• Look up control board LED codes to guide component testing or replacement.

Cost-Benefit Considerations For Repair Vs Replacement

Decide between repair and replacement based on furnace age, efficiency, and repair cost. If an Armstrong furnace is over 15–20 years old, or if repair costs exceed 50% of a new system price, replacement with a high-efficiency unit may be more economical.

Newer furnaces offer improved efficiency, quieter operation, and modern safety and diagnostic features. Incentives, rebates, or energy savings can offset installation costs over time.

Resources And Manuals

Owner manuals and error code charts from Armstrong Air provide model-specific guidance; these are available on the manufacturer’s website or through HVAC service providers. Local utility or energy-efficiency programs can also offer rebates and contractor referrals.

For gas leaks, call the gas company immediately. For electrical hazards or complex controls, contact a licensed electrician or HVAC technician rather than attempting advanced repairs alone.

Key Takeaways And Next Steps

When an Armstrong Air furnace is not igniting, follow a logical troubleshooting sequence: check power and thermostat, inspect vents and filters, observe ignitor and flame sensor action, test gas supply and valve response, and consult control board codes. Simple fixes often resolve ignition failures, but safety-critical or gas-related issues require a professional technician.

Document observed symptoms, control board codes, and any DIY steps taken before calling a technician to speed diagnostics and reduce service time and cost.