Armstrong SX90 Gas Furnace Issues with Blower and Ignition: How to Fix

Armstrong SX90 Gas Furnace Issues with Blower and Ignition: How to Fix

The Armstrong SX90 gas furnace is a trusted model known for its durability, high efficiency, and consistent heating performance. However, like any HVAC equipment, it can occasionally experience issues—especially related to the blower motor and ignition system. These components play critical roles in air circulation and combustion, so when they malfunction, comfort and safety are at risk. The most common Armstrong air gas furnace troubleshooting procedures will be covered in this guide, along with common blower and ignition problems, their efficient fixes, and advice on preventive maintenance. Understanding your Armstrong air gas furnace parts and how they interact can help minimize downtime and extend your unit’s lifespan.

Common Blower and Ignition Problems in Armstrong SX90 Gas Furnaces

Even a high-performance unit like the Armstrong SX90 can face performance hiccups over time due to wear, electrical issues, or lack of maintenance. Here are some of the most frequent blower and ignition problems homeowners or commercial users encounter:

Blower Motor Not Starting

If the furnace hums but the blower motor doesn’t run, the issue could be linked to a faulty capacitor, control board, or the blower relay. The blower is essential for circulating warm air through the ducts, and any malfunction can result in poor heating or no airflow at all.

Possible Causes:

• Blown fuse or tripped circuit breaker

• Faulty motor capacitor

• Damaged blower motor bearings

• Worn-out or corroded wiring connections

  
  

Related Armstrong Air Gas Furnace Parts: Blower motor assembly, motor capacitor, furnace control board.

Weak or Intermittent Airflow

If the blower runs but produces little airflow, it may be due to dust buildup, restricted air filters, or a failing motor. In some cases, fan speed settings on the control board may also need adjustment.

Possible Causes:

• Dirty air filters or evaporator coil

• Failing blower motor winding

• Obstructed return vents or ductwork

Regular maintenance of Armstrong air gas furnace parts, especially filters and motor assemblies, helps maintain airflow efficiency.

Ignition System Failing to Start

When the ignition system fails, the burners won’t light, and the furnace may enter a safety lockout mode. This is a common issue in older SX90 models using hot surface igniters or intermittent spark ignition systems.

Possible Causes:

• Cracked or burnt-out igniter

• Faulty flame sensor

• Control board malfunction

• Gas valve not opening

  
  

Related Armstrong Air Gas Furnace Parts: Hot surface igniter, flame sensor, ignition module, gas valve assembly.

Furnace Starts but Shuts Down Quickly

If your Armstrong SX90 starts up but stops within seconds, the problem may be with the pressure switch, limit switch, or flame sensor. These parts ensure safe operation by verifying air pressure, temperature, and flame presence.

Possible Causes:

• Blocked flue vent

• The flame sensor is dirty.

• The pressure switch is broken.

Replacing these safety sensors with genuine Armstrong air gas furnace parts ensures consistent and safe operation.

Blower Runs Constantly

A continuously running blower can be caused by a stuck relay, misconfigured thermostat, or a control board malfunction. This can lead to energy waste and uneven temperature control.

Possible Causes:

• Thermostat set to “Fan On” instead of “Auto”

• Stuck relay on the control board

• Faulty limit switch

  
  

Steps to Fix Blower Motor and Ignition Problems in the SX90 Furnace

Now that you know the common causes, let’s go step-by-step through the troubleshooting and repair process for the Armstrong SX90 gas furnace. Always turn off the furnace and disconnect power before starting any inspection.

# Step 1: Check the Power Supply and Thermostat

Before diving into component-level diagnostics, confirm that the furnace is receiving power.

• Ensure the breaker isn’t tripped.

• Verify that the thermostat is set to “Heat” mode and the fan to “Auto.”

• Replace thermostat batteries if necessary.

If the system remains unresponsive, the issue may be in the control board or wiring—both critical Armstrong air gas furnace parts that regulate communication and power flow.

# Step 2: Inspect and Clean the Air Filter

A clogged filter restricts airflow, causing the blower motor to overwork or overheat.

• Switch the furnace off.

• Remove and inspect the air filter.

• Replace it if it has become filthy or covered with dust.

Routine filter maintenance prevents stress on connected Armstrong air gas furnace parts, improving longevity.

# Step 3: Examine the Blower Motor

If the blower doesn’t start, remove the furnace access panel to locate the blower motor assembly.

• Check the capacitor with a multimeter—if it shows zero or fluctuating readings, replace it.

• Spin the blower wheel manually. If it feels stiff, the motor bearings might be seizing up.

• Inspect wiring for loose or burnt connectors.

If the motor fails continuity, replace it with a manufacturer-rated Armstrong air gas furnace part to restore proper airflow and speed control.

# Step 4: Test the Igniter

The ignition system is the heart of the furnace’s heating sequence.

• Remove the igniter carefully and inspect it for cracks or white residue.

• Use a multimeter to check resistance. A healthy igniter typically reads between 40 and 200 ohms.

• Replace the igniter if it’s outside this range or visibly damaged.

Handle with care—finger oils can damage the element. Always choose original Armstrong air gas furnace parts for reliability.

# Step 5: Clean Up the Flame Sensor

A dirty flame sensor can misread ignition and shut off the gas valve prematurely.

• Turn the furnace off and remove the sensor using a nut driver.

• Gently clean it with fine-grit sandpaper or steel wool.

• Reinstall it and test the ignition sequence.

This simple step often fixes intermittent startup issues without full Armstrong air gas furnace parts replacement.

# Step 6: Verify Gas Flow

If the igniter glows but the burners don’t light, the gas valve may not be opening.

• Ensure the gas supply valve is on.

• Listen for the click of the valve during ignition.

• If there’s no sound or gas smell, test the valve with a multimeter.

Replace with a compatible Armstrong air gas furnace part to ensure safe combustion control.

# Step 7: Check the Pressure and Limit Switches

These safety components regulate airflow and prevent overheating.

• Use a manometer to check proper pressure switch operation.

• Test the limit switch for continuity.

• Replace defective switches to restore normal cycling.

Genuine Armstrong air gas furnace parts maintain accuracy and safety in these critical systems.

# Step 8: Reset or Replace the Control Board

If the blower and ignition sequence fail despite all checks, the control board could be defective.

• Turn off power for 30 seconds to reset it.

• Inspect for burnt or corroded contacts.

• If the board doesn’t respond, order a compatible Armstrong air gas furnace replacement board.

  
  

# Step 9: Test the Full Heating Cycle

Once all components are checked or replaced:

• Turn on the furnace and set the thermostat to heat.

• Observe the ignition process—watch for burner ignition, steady flame, and consistent blower operation.

• Listen for unusual noises or short cycling, which may indicate further airflow or control issues.

If the furnace now runs smoothly, you’ve successfully completed the Armstrong air gas furnace troubleshooting process.

Preventive Maintenance Tips for the Armstrong SX90 Furnace

Routine maintenance is the key to extending the lifespan of your Armstrong SX90 gas furnace and preventing costly repairs. Regular care ensures efficient airflow, reliable ignition, and safe operation during peak heating months.

• Replace Air Filters Regularly: Dirty filters restrict airflow, forcing the blower motor to work harder. Replace filters every 1–3 months to maintain proper ventilation.

• Clean Blower and Burner Assembly: Dust and soot can accumulate on components, affecting performance. Clean them annually to ensure smooth operation.

• Inspect Electrical Connections: Loose or corroded wiring can cause ignition failures or short cycling. Tighten all terminals and check for discoloration or wear.

• Lubricate Moving Parts: If your Armstrong furnace blower motor isn’t sealed, lubricate bearings once a year to reduce friction and noise.

• Check Safety Components: Test the limit switch, pressure switch, and flame sensor to ensure accurate readings and safety compliance.

• Use Genuine Armstrong Air Parts: Always choose genuine components for replacements to ensure compatibility and long-term reliability.

  
  

By following these maintenance steps, your Armstrong SX90 furnace will deliver consistent heating, reduced energy costs, and fewer unexpected breakdowns throughout its service life.

Maintaining the Armstrong SX90 gas furnace involves understanding how the blower and ignition systems work together. Regular cleaning, prompt repairs, and the use of authentic Armstrong air gas furnace parts ensure reliable operation throughout the heating season. Whether you’re replacing a worn blower motor, testing an igniter, or cleaning a flame sensor, following proper troubleshooting steps keeps your unit efficient and safe. For complex repairs, always consult a certified HVAC technician familiar with Armstrong air parts to ensure long-term performance, energy efficiency, and comfort in your home or commercial space.

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