Armstrong Furnace Error Codes: Common Issues and How to Fix Them

Armstrong furnace error codes are diagnostic signals displayed via a blinking LED light on the control board. Each code corresponds to a specific issue, such as ignition failure, pressure switch problems, or overheating. By counting the number of blinks and referring to the error code chart, you can identify what’s wrong with your furnace. These codes help homeowners and HVAC technicians diagnose and fix issues more efficiently.

To reset your Armstrong furnace, turn off the power switch or shut off the breaker for about five minutes. This allows the system to clear any error codes. After restoring power, set your thermostat to heat mode and adjust the temperature. If the furnace starts working normally, the issue may have been temporary. However, if the error code returns, further troubleshooting or professional service is required.

A pressure switch that’s stuck open usually indicates restricted airflow, which can be caused by blocked vents, a clogged filter, or a malfunctioning inducer motor. A pressure switch stuck closed may result from wiring issues or a faulty switch. In either case, checking the filter, vents, and tubing can help determine the cause before calling an HVAC technician.

If your furnace isn’t igniting, the most common reasons include a dirty or faulty flame sensor, a defective ignitor, or a gas supply issue. Cleaning the flame sensor with fine-grit sandpaper and checking the gas valve can sometimes resolve the issue. If the ignitor is cracked or broken, it will need to be replaced. If you smell gas or suspect a supply problem, call a professional immediately.

Overheating is often caused by restricted airflow due to a dirty air filter, blocked vents, or a malfunctioning blower motor. Replacing the filter and ensuring all vents are open can help. If the issue persists, the high-limit switch may need replacement. A professional HVAC inspection can pinpoint the exact cause and prevent further damage.

A furnace that frequently shuts off (short cycles) may have a clogged filter, an overheating issue, or a malfunctioning thermostat. Replacing the filter and checking the thermostat settings can help. If the high-limit switch is tripping repeatedly, it’s best to call a technician to diagnose airflow problems or possible heat exchanger issues.

Flame loss errors can occur due to a dirty flame sensor, low gas pressure, or a faulty ignition system. Cleaning the flame sensor is often a simple fix. However, if the problem persists, checking for gas flow interruptions or burner issues may be necessary. Persistent flame loss errors should be assessed by an HVAC technician to avoid heating disruptions.

Some minor issues, such as a dirty flame sensor or a clogged air filter, can be fixed by homeowners with basic maintenance. However, more complex issues, like pressure switch failures or rollout switch errors, require professional diagnosis and repair. If you’re unsure, it’s always safer to call an HVAC technician to prevent potential damage or safety hazards.

It’s recommended to schedule professional maintenance at least once a year, ideally before the heating season begins. Regular tune-ups help prevent common furnace issues, extend the unit’s lifespan, and ensure optimal efficiency. In addition to professional servicing, homeowners should replace air filters every 1–3 months and keep vents clear to maintain proper airflow.

If your furnace is over 15–20 years old and frequently breaks down, replacement may be more cost-effective than continuous repairs. Signs that it’s time for a new unit include rising energy bills, uneven heating, loud noises, and expensive repairs that exceed half the cost of a new furnace. Upgrading to a newer, more efficient model can improve comfort and reduce long-term energy costs.