Carrier Furnace Error Codes List and Troubleshooting

The Carrier furnace error codes list helps homeowners and technicians quickly diagnose issues, interpret flashing LED patterns, and decide whether a reset or service call is needed. This guide covers common Carrier error codes, their meanings, troubleshooting steps, and preventive maintenance tips to keep furnaces running efficiently.

Code/Indicator	Symptom	Probable Cause
Ready/Service LED Flash 1	No heat/Normal operation	System enabled/Pressure switch open
LED Flash 2	Ignition failure	Ignitor issue or gas valve
LED Flash 3	Flame sensed then lost	Flame failure or airflow problem
LED Flash 4	Pressure switch stuck	Blocked vent or switch failure
LED Flash 5	High limit/trip	Overheating or blocked return
LED Flash 6	Control board lockout	Repeated ignition failures

How Carrier Furnace Error Codes Work

Carrier furnaces use an LED on the control board to communicate status and faults through a sequence of flashes or steady lights. Each model family (e.g., Infinity, Performance, Comfort) may show codes slightly differently, but the underlying diagnostics follow similar patterns.

Understanding the code display helps prioritize repairs and prevent unnecessary service calls. Attention to code patterns and accompanying symptoms such as no heat, blower behavior, or unusual noises improves troubleshooting accuracy.

Where To Find The Error Codes On Carrier Furnaces

The error codes are usually visible on the control board inside the furnace access panel or through a diagnostic connector on some models. For Infinity systems, codes may also display on the thermostat or an outdoor unit.

Always turn off power before removing the service panel. Photograph the LED pattern or note the flash count and any steady LEDs to provide accurate information to a technician if needed.

Common Carrier Furnace Error Codes And Meanings

1 Flash (System Standby/Normal)

One flash typically indicates normal system operation or standby. It may also represent the control board’s heartbeat signal. No corrective action is usually required.

2 Flashes (Ignition Failure)

Two flashes usually indicate an ignition failure where the furnace attempted to ignite but the flame was not established. Common causes include a failed ignitor, faulty flame sensor, or gas supply issues.

3 Flashes (Flame Sensed Then Lost)

Three flashes often mean the flame was detected then dropped out. This can be caused by intermittent gas supply, flame sensor fouling, or draft/venting problems.

4 Flashes (Pressure Switch Open/Failure)

Four flashes indicate a pressure switch that did not close or opened unexpectedly. This can point to blocked combustion air intake, clogged venting, or a failed pressure switch or inducer motor.

5 Flashes (Limit/Overheat)

Five flashes correspond to a high-limit switch tripping due to overheating. Causes include restricted airflow from dirty filters, blocked return registers, or a failing blower motor.

6 Flashes (Control Lockout)

Six flashes often reflect a control board lockout after repeated ignition attempts or a critical safety fault. Resetting may temporarily restore operation, but recurring lockouts require professional diagnosis.

7+ Flashes And Model-Specific Codes

Certain models show additional flash patterns or combinations to indicate issues like low flame signal, thermistor failure, or communication faults between modules. Always consult the model-specific service manual when in doubt.

Troubleshooting Steps For Each Code

Initial Safety Checks

Before any troubleshooting, confirm the furnace has power and gas supply. Verify the thermostat setting and circuit breakers. If any smell of gas exists, evacuate and call the gas utility or 911 immediately.

For Ignition Failure (2 Flashes)

Check the ignitor for visible cracks and test continuity with a multimeter. Clean the flame sensor gently with fine emery cloth. Verify the gas valve is supplying manifold pressure and the gas line is open.

For Flame Loss (3 Flashes)

Clean the flame sensor and inspect burner ports for dirt or corrosion. Ensure the venting is clear and that the inducer motor is operating steadily during ignition sequence.

For Pressure Switch Issues (4 Flashes)

Inspect the vent pipes for nests, ice, or debris. Check the vacuum tubing to the pressure switch for cracks or disconnections. Measure the inducer motor vacuum if accessible.

For High Limit Trips (5 Flashes)

Replace dirty filters, ensure return vents are unobstructed, and inspect blower wheel for debris. Verify blower operation and capacitor health. Confirm adequate airflow in ductwork.

For Control Lockout (6 Flashes)

Attempt a single reset by turning power off for 30 seconds and then on. If lockouts persist, collect auxiliary symptoms (sounds, recent repairs) and schedule professional service to inspect gas pressure, control board function, and safety circuits.

How To Safely Reset A Carrier Furnace

Resetting may clear transient faults but should be done cautiously. Turn the thermostat to OFF, switch the furnace power at the service switch or breaker to OFF, wait 30 seconds, then restore power and set the thermostat back to heat. Avoid repeated hard resets if the same code returns.

Document the code and behavior before resetting to help a technician diagnose persistent problems. Repeated lockouts indicate underlying issues that require repair.

When To Call A Professional Technician

If codes persist after basic troubleshooting, or if there is any sign of gas smell, carbon monoxide alarm activation, or repeated lockouts, contact a qualified HVAC technician. Professional diagnosis is recommended for gas valve, control board, inducer motor, and combustion analysis tasks.

Technicians have access to model-specific service manuals, combustion analyzers, and replacement parts, and can perform safe procedures like gas pressure testing and control board replacement.

Preventive Maintenance To Reduce Error Codes

Regular maintenance lowers the frequency of error codes. Recommended tasks include changing filters every 1–3 months, annual professional tune-ups, cleaning burners and flame sensors, and inspecting venting and condensate traps.

Sealing duct leaks, ensuring adequate return airflow, and maintaining proper thermostat calibration also reduce stress on furnace components and prevent overheating and ignition issues.

Model-Specific Notes And Variations

Carrier Infinity models often integrate diagnostics with smart thermostats and the Carrier app, allowing remote access to system status and error codes. Performance and Comfort series may rely primarily on control board LED patterns.

Always reference the furnace model number and the Carrier service manual for precise code definitions and troubleshooting flowcharts. Model-specific nuances can change the interpretation of a given flash pattern.

Common Misdiagnoses And Pitfalls

Replacing the ignitor or control board without confirming the root cause is a common mistake that can lead to repeated failures. Many ignition and flame issues are caused by dirty flame sensors, airflow restrictions, or intermittent gas supply rather than component failure.

Overlooking simple items such as clogged condensate traps, blocked vents, or disconnected pressure switch tubing can result in unnecessary parts replacement and higher repair bills.

Helpful Tools For Diagnosing Carrier Furnace Codes

• Multimeter for continuity and voltage checks
• Small mirror and flashlight for visual inspection
• Fine emery cloth for cleaning flame sensors
• Combustion analyzer for professional use
• Thermometer and clamp meter to check blower performance

Frequently Asked Questions About Carrier Furnace Error Codes

How Long Should A Reset Fix The Problem?

A reset can clear transient errors for a short time, but recurring faults usually indicate a persistent issue needing repair. Use reset only after documenting the error code and symptoms.

Are Carrier Error Codes The Same Across All Models?

Core meanings are similar, but flash patterns and additional codes may vary by model. Always consult the model-specific manual or Carrier technical literature for exact definitions.

Can Homeowners Fix All Carrier Furnace Problems?

Homeowners can perform visual inspections, filter changes, flame sensor cleaning, and basic resets. Tasks involving gas pressure, control board replacement, or combustion adjustments should be left to trained professionals.

Resources And Where To Find Model Manuals

Carrier publishes owner and service manuals on its official website. Local authorized Carrier dealers and certified HVAC technicians can provide model-specific guidance and diagnostic support. Online forums and instructional videos can assist with basic maintenance but should not replace professional service for gas-related work.

Keep the furnace model and serial number handy when searching for documentation or contacting support.

Key Takeaways

Recognize the LED flash patterns and document them before resetting. Troubleshoot common causes like dirty flame sensors, blocked vents, and airflow restrictions first. Call a professional for gas, combustion, or control board issues and for recurring lockouts to ensure safe, long-term operation.