Comfortmaker Furnace Error Codes and Troubleshooting Guide

The following guide explains Comfortmaker furnace error codes, what each code means, common causes, basic troubleshooting steps, and when to call a qualified HVAC technician. This resource helps homeowners quickly identify issues, perform safe checks, and understand diagnostics to reduce downtime and unnecessary repair costs.

Code	LED Pattern/Display	Meaning	Common Causes
1 Blink	Slow Blink	Open High Limit	Blocked airflow, dirty filter, failing limit switch
2 Blinks	Slow Blink	Main Burner Lockout	Ignition failure, gas supply, flame sensed issues
3 Blinks	Slow Blink	Pressure Switch Fault	Blocked venting, bad inducer, faulty switch
4 Blinks	Slow Blink	Flame Loss / Flame Failure	Dirty flame sensor, gas valve, ignition instability
5 Blinks	Slow Blink	Open Rollout Or Flame Rollout	Cracked heat exchanger, blocked vent, improper combustion
6 Blinks	Slow Blink	Low Voltage Or Control Board Fault	Transformer, wiring, control board issues

How Comfortmaker Furnace Error Codes Work

Comfortmaker furnaces use an LED indicator or digital display to communicate system status and faults. Error codes are delivered as blink patterns, numeric readouts, or both, and are designed to guide diagnostics by indicating the subsystem with a fault. Understanding the blink patterns and associated technical bulletins accelerates troubleshooting.

Locating The Diagnostic LED And Control Board

The diagnostic LED and control board are usually behind the furnace access panel on the front or side of the unit. Before accessing the panel, turn off power at the switch or breaker. The control board label and wiring diagram often list blink code definitions for the specific model.

Common Comfortmaker Error Codes And Their Meanings

1 Blink — High Limit Open

One blink typically indicates an open high-limit or overtemperature condition. The limit switch opens to protect the furnace when the heat exchanger gets too hot.

Common causes: dirty air filter, blocked return or supply vents, closed registers, malfunctioning blower motor, or a failed limit switch.

Troubleshooting steps: Inspect and replace the air filter, check airflow at vents, ensure blower runs during heat call, and inspect the limit switch wiring. If airflow and blower are normal, a technician should test the limit switch and heat exchanger temperatures.

2 Blinks — Main Burner Lockout / Ignition Failure

Two blinks generally indicate ignition failure or lockout after repeated unsuccessful ignition attempts. The control will typically attempt ignition several times before locking out.

Common causes: no gas supply, faulty gas valve, weak ignition spark or hot surface ignitor failure, faulty flame sensor, or blocked or disconnected gas piping.

Troubleshooting steps: Verify the gas valve and supply are open, check for error history on the control board, inspect ignitor for cracks or glow (for hot surface ignitors), clean the flame sensor, and check wiring connections. If uncertain, call a licensed HVAC technician due to gas safety risks.

3 Blinks — Pressure Switch Or Venting Fault

Three blinks often indicate a pressure switch problem or blocked venting. The pressure switch ensures the inducer motor is creating sufficient draft before ignition.

Common causes: clogged condensate drain, blocked intake or exhaust vent, failed inducer motor, or a defective pressure switch hose.

Troubleshooting steps: Inspect intake/exhaust for obstructions (bird nests, leaves, ice), check inducer motor operation, test the rubber hose to the pressure switch for cracks or blockages, and confirm drain lines are clear. Replace the pressure switch only after verifying venting and inducer operation.

4 Blinks — Flame Loss During Operation

Four blinks point to intermittent flame loss after ignition, which triggers a safety shutdown. The control monitored flame signal and shuts down if continuous flame is not detected.

Common causes: dirty flame sensor, flame rectification issues, gas pressure fluctuation, or loose electrical connections.

Troubleshooting steps: Turn off power and clean the flame sensor with fine-grit sandpaper, tighten gas and wiring connections, and check for flame stability on relight. If the issue continues, a technician should measure gas pressures and inspect ignition components.

5 Blinks — Rollout Or Overfire Condition

Five blinks usually indicate a rollout or combustion gas entering the cabinet due to blockages or heat exchanger problems. Rollout switches open to prevent fire hazards.

Common causes: blocked heat exchanger, cracked heat exchanger, improper combustion, flue blockage, or excessive backpressure.

Troubleshooting steps: Immediately turn off the furnace and do not operate until inspected. A qualified technician should examine the combustion chamber, heat exchanger, and venting. Heat exchanger cracks require professional replacement due to carbon monoxide risk.

6 Blinks — Control Board Or Low Voltage

Six blinks may indicate a control board fault or low incoming voltage. Controls can report faults when internal diagnostics detect issues or insufficient power to operate safely.

Common causes: failed control board, transformer failure, loose wiring, or inadequate home electrical supply.

Troubleshooting steps: Check the 24VAC supply at the control with a multimeter, verify transformer output, inspect connections for corrosion, and look for visible board damage. Replace the control board or transformer if tests confirm failure.

How To Read Blink Codes And Record Diagnostics

Turn the thermostat to heat and observe the LED during startup and operation. Count the slow or fast blinks and record sequences. Some controls display a series (e.g., 3 blinks, pause, 3 blinks) indicating the same code repeated. Documenting the pattern and any thermostat settings helps technicians diagnose remotely.

Safe Basic Troubleshooting Checklist

• Turn off power at switch or breaker before removing panels.
• Replace a dirty air filter and ensure return vents are open.
• Inspect combustion air and exhaust vents for obstructions.
• Check the furnace switch, thermostat batteries, and thermostat wiring.
• Clean the flame sensor gently with fine sandpaper; avoid bending it.
• Reset the system by turning power off for 30 seconds and powering back on; don’t cycle repeatedly.

When To Call A Professional HVAC Technician

A professional is required for complex or unsafe conditions, including persistent ignition failures, suspected heat exchanger cracks, gas valve replacement, venting repairs, control board replacement, or any carbon monoxide concerns. Do not attempt gas valve or combustion chamber repairs without proper certification.

Tools And Materials For Homeowner Checks

Common tools for safe homeowner checks include a replacement 1-inch pleated filter, a flashlight, a multimeter for basic voltage checks, a soft brush or fine-grit sandpaper for flame sensor cleaning, and a small vacuum for dust removal. Avoid internal repairs beyond cleaning and visual inspections.

Preventive Maintenance To Avoid Error Codes

Regular maintenance reduces fault frequency. Recommended actions include changing the air filter every 1–3 months, annual professional tune-ups in fall, cleaning burners and flame sensors, checking and clearing venting, and verifying thermostat calibration.

Understanding Model-Specific Variations

Comfortmaker models vary in exact blink patterns and digital code displays; always check the model’s data plate and installation manual for the definitive fault table. Manufacturers sometimes change diagnostics across control revisions, so match the code to the specific model number.

Carbon Monoxide And Safety Considerations

Any signs of soot, rust-colored streaking, strong furnace odors, or symptoms such as headaches, nausea, or dizziness require immediate attention. Install a carbon monoxide alarm near sleeping areas and follow manufacturer warnings. If the furnace is suspected of leaking combustion gases, shut off the unit and ventilate the area while contacting emergency services or a HVAC pro.

Sample Troubleshooting Flow For A 2-Blink Ignition Failure

1. Confirm thermostat calls for heat and the inducer runs.
2. Observe ignitor behavior: does it glow or spark?
3. Clean the flame sensor and retry a reset cycle once.
4. Check gas supply at other appliances to confirm the house gas is on.
5. If ignition still fails, contact a licensed technician for gas valve, ignition module, or control board service.

How To Report Error Codes To A Technician

When contacting a technician, provide the furnace model number, serial number, exact LED blink pattern, any recent maintenance, symptoms like unusual noises, and what troubleshooting steps were taken. This information helps the technician bring the right parts and expedite repairs.

Replacement Parts And Warranty Considerations

Verify warranty status before replacing parts; many components are covered under limited warranties. Use OEM parts or manufacturer-approved components to maintain safety and warranty compliance. A certified technician can verify part numbers and source correct replacements.

Additional Resources And Manuals

Comfortmaker owners should download the model-specific installation and service manual from the official distributor or manufacturer website. Manufacturer technical bulletins and safety recalls are also important to review periodically.

Key Takeaways

Comfortmaker furnace error codes provide crucial diagnostic clues: blink patterns point to limits, ignition, pressure, flame loss, rollout, or control faults. Homeowners can perform safe basic checks like replacing filters, cleaning the flame sensor, and clearing vents. For gas-related, combustion, or heat exchanger issues, always contact a licensed HVAC technician to ensure safety and proper repairs.