Coleman Furnace Troubleshooting: Flame and Status Light Codes

The following guide explains common Coleman furnace light codes, how to read the control board LED flashes, and practical troubleshooting steps for safe, effective diagnostics. It focuses on the most frequent error codes, what they mean, and the next actions a homeowner or technician should consider. Never attempt repairs beyond basic checks unless qualified.

LED Code	Flashes/Pattern	Common Meaning
1 Flash	Single blink repeating	Normal Operation / Standby
2 Flashes	Two blinks repeating	Pressure Switch Open / Airflow Issue
3 Flashes	Three blinks repeating	Ignition Lockout / Failed Ignition
4 Flashes	Four blinks repeating	Open High Limit / Overtemperature
5 Flashes	Five blinks repeating	Flame Sense Failure / Loss Of Flame Signal
6 Flashes	Six blinks repeating	Low Flame Current / Flame Out During Operation
7 Flashes	Seven blinks repeating	Gas Valve Circuit Or Polarity Fault
8 Flashes	Eight blinks repeating	Limit Circuit Or Control Board Fault

How Coleman Furnace Light Codes Work

Coleman furnaces use a control board with a status LED to communicate operating conditions and faults through a pattern of flashes. The LED patterns represent diagnostic codes that help isolate mechanical, electrical, or safety issues.

Understanding these light codes enables quicker troubleshooting, reduces diagnostic time, and helps determine whether a simple homeowner fix or professional service is required. Always verify the exact model’s service manual because codes can slightly differ across control boards.

Reading The LED: Steps Before Diagnosing

Begin by ensuring power to the furnace is stable and the thermostat calls for heat so the control board is active and producing a pattern. Record the blink sequence over a 30–60 second period.

Count short blinks separated by a pause as one code. If multiple sequences appear, document each pattern and whether a steady light accompanies blinks. This information is crucial when consulting manuals or communicating with a technician.

Common Coleman Furnace Light Codes And Meanings

1 Flash — Normal Operation Or Standby

A repeating single flash typically means the control board is in normal standby or operating without detected faults. If the system won’t produce heat despite this, check the thermostat settings, filter, and pilot/ignition sequence.

2 Flashes — Pressure Switch Or Airflow Problem

Two flashes often indicate an open pressure switch or restricted venting/airflow problem. The pressure switch confirms proper inducer operation and combustion venting.

Common causes include a clogged air filter, blocked combustion air intake or exhaust, kinked PVC vent pipes, or a failing inducer motor. Check and replace filters, inspect vents, and confirm inducer operation before calling a professional.

3 Flashes — Ignition Lockout / Failed Ignition

Three flashes point to repeated ignition failures leading to lockout. Possible culprits are dirty burners, faulty ignitor or pilot assembly, gas supply issues, or flame sensor contamination.

Basic homeowner steps include verifying the gas supply, ensuring burner ports are clean, and gently cleaning the flame sensor with fine emery cloth. If the ignition module or gas valve fails, a certified technician should handle replacement.

4 Flashes — Open High Limit Or Overtemperature

Four flashes signal the high-limit switch opened due to overheating. Causes include blocked return air, dirty filters, closed supply vents, or a failing blower motor.

Inspect and replace clogged filters, ensure registers are open, and listen for unusual blower operation. Persistent limit trips require professional inspection of heat exchanger and blower operation to prevent safety hazards.

5 Flashes — Flame Sense Failure

Five blinks indicate the control lost a flame signal during ignition or flame detection period. This is commonly caused by a dirty flame sensor, weak flame, or wiring/grounding issues.

Cleaning the flame sensor and confirming proper burner operation often resolves the issue. If cleaning doesn’t help, the sensor or control board input may need replacement.

6 Flashes — Low Flame Current Or Flame Out

Six flashes typically mean low flame current or flame extinguishment during operation. This can result from low gas pressure, partial blockage in orifices, or a failing gas valve.

Gas pressure checks and valve function tests are required, which should be performed by a licensed technician. Do not attempt gas adjustments without proper certification.

7 Flashes — Gas Valve Or Polarity Fault

Seven blinks often point to issues with the gas valve circuit, such as improper polarity, wiring problems, or a defective valve. Incorrect thermostat wiring or transformer secondary polarity can trigger this code.

Verify thermostat wiring and transformer connections before replacing the gas valve. Electrical measurements and safe handling by a professional are advised.

8 Flashes — Limit Circuit Or Control Board Fault

Eight flashes may indicate a limit circuit fault or an internal control board problem. This is a broader error that can require component-level diagnostics.

Inspect limit switches, wiring harnesses, and connectors for corrosion or damage. If the control board is suspected, replacement or professional repair is typically necessary.

Diagnostic Flow: Quick Checklist For Homeowners

• Power And Thermostat: Confirm furnace has power and thermostat is set correctly.
• Filters And Airflow: Replace filters and ensure vents are open to prevent limit or pressure faults.
• Venting And Inducer: Inspect combustion venting and inducer operation for two-flash issues.
• Flame Sensor: Clean flame sensor with fine abrasive if experiencing flame sense codes.
• Gas Supply: Verify gas is on and other gas appliances function; for gas pressure issues call a pro.
• Record Codes: Note exact blink pattern, any accompanying steady lights, and furnace behavior for technician handoff.

When To Call A Technician

Contact a licensed HVAC technician when codes indicate gas valve failure, recurring ignition lockouts after basic cleaning, control board faults, or when safe electrical or gas diagnostics are required.

Immediate professional service is essential if there is any smell of gas, visible damage to the heat exchanger, or repeated high-limit trips to protect occupants and equipment.

Resetting The Furnace: Safe Practices

Most Coleman furnaces can be reset by cycling power at the breaker or using a reset button if provided. Allow at least 30 seconds before restoring power to clear the control’s memory.

Resetting may temporarily clear an error but does not fix the underlying cause. If the same code returns, follow the diagnostic steps or call a technician. Repeated resets can mask progressive faults and lead to unsafe conditions.

Maintenance Tips To Prevent Error Codes

• Replace air filters every 1–3 months depending on usage and indoor air quality.
• Schedule annual professional tune-ups to inspect burners, flame sensors, gas pressure, and venting.
• Keep intake and exhaust vents clear of debris, snow, or obstructions.
• Ensure proper thermostat wiring and batteries; a faulty thermostat can create repeated call issues.
• Listen for unusual sounds such as rattles, hums, or prolonged inducer spin-up which can indicate failing components.

Model Differences And Where To Find The Exact Codes

Coleman furnaces may use different control boards across model lines, so the LED code meanings can vary slightly. Always consult the furnace’s white data plate and the OEM service manual for model-specific decoding and safety instructions.

Service manuals and wiring diagrams are available from manufacturer websites, HVAC supply distributors, or through a licensed contractor. Having the model and serial number ready speeds up accurate diagnosis.

Safety And Liability Considerations

Working inside furnaces exposes individuals to electrical shock, gas hazards, and combustion products. Basic checks like replacing filters and cleaning flame sensors are commonly safe for homeowners, but component replacement, gas adjustments, and electrical repairs should be left to certified professionals.

For any suspected heat exchanger cracks, corrosion, or persistent carbon monoxide concerns consult a professional immediately and consider evacuating the premises until the system is deemed safe.

Frequently Asked Questions

Can Cleaning The Flame Sensor Fix Most Ignition Codes?

Yes, a dirty flame sensor is a frequent cause of ignition and flame-detection codes. Cleaning the sensor with fine abrasive or steel wool often restores proper flame detection.

How Long Should I Wait After Resetting A Furnace?

Wait 30–60 seconds after power cycling to allow the control to fully reset and go through the start sequence. If the same code reappears, further diagnosis is required.

Are All Blink Codes The Same Across Coleman Furnaces?

No. While many codes are similar, differences exist by control board and model. Always verify with the specific unit’s service literature.

Useful Resources And Next Steps

For accurate code charts, consult the furnace’s service manual or the Coleman/Carrier technical support portal. If the code indicates a gas or control fault and basic maintenance doesn’t resolve it, schedule a certified HVAC technician to perform safe, code-compliant repairs.

Documenting the blink pattern, model number, and any recent events (power outages, storms, maintenance) will help the technician diagnose and fix the issue faster.