Decoding Rheem Furnace Light Codes: A Comprehensive Guide for Homeowners

Rheem furnaces are a popular heating solution across many American homes, known for their reliability and efficiency. Like many modern HVAC systems, Rheem furnaces use diagnostic light codes to communicate operational status and troubleshoot issues. These blinking light codes are essential for both homeowners and technicians to understand system performance and identify malfunctions swiftly. Recognizing and interpreting Rheem furnace light codes can save time and reduce repair costs, ensuring comfortable and safe heating throughout the colder months.

Light Code	Error Description	Recommended Action
1 Blink	Pressure Switch Open	Check venting and pressure switch for blockages or damage
2 Blinks	Pressure Switch Closed	Inspect pressure switch and wiring
3 Blinks	Ignition Lockout	Reset unit and verify gas supply and ignition system
4 Blinks	Flame Sense Failure	Clean flame sensor or replace if faulty
5 Blinks	Open High Limit Switch	Check airflow and replace high limit switch if necessary

How Rheem Furnace Light Codes Work

Rheem furnaces employ an LED status light on the control board that flashes specific patterns to indicate operational conditions or faults. Each sequence corresponds to a particular diagnostic code, designed to pinpoint issues with components like the ignition system, pressure switches, or safety sensors.

The light codes typically flash in a pattern of blinks followed by a pause, repeating until the problem is addressed or the furnace resets. Understanding these signals helps users identify problems promptly without needing immediate professional intervention.

Common Rheem Furnace Light Codes and Their Meanings

1 Blink: Pressure Switch Open

This code signifies the pressure switch has failed to close during startup, indicating potential venting problems or obstructions in the air intake or exhaust pathways. The pressure switch ensures the furnace has proper airflow before ignition.

Recommended Action: Inspect vent pipes for blockages like debris or bird nests. Also, examine the pressure switch tubing for cracks or disconnections.

2 Blinks: Pressure Switch Closed

This indicates the pressure switch remains closed when it should be open during the startup sequence, often caused by a faulty switch or wiring issues, potentially affecting furnace safety.

Recommended Action: Test the pressure switch with a multimeter and inspect wiring for damage or loose connections.

3 Blinks: Ignition Lockout

This pattern means the furnace attempted to ignite multiple times but failed, triggering a safety lockout to prevent gas build-up. Causes could include no gas supply, faulty ignitor, or gas valve problems.

Recommended Action: Verify the gas supply is turned on, inspect the ignitor for cracks or wear, and check the gas valve and related wiring.

4 Blinks: Flame Sense Failure

This code signals the burner flame is not being detected, often due to a dirty or faulty flame sensor. The sensor’s role is to confirm ignition to the control board.

Recommended Action: Clean the flame sensor using fine sandpaper or steel wool and check connections. Replace the sensor if cleaning doesn’t resolve the issue.

5 Blinks: Open High Limit Switch

This indicates the furnace is overheating, causing the high limit switch to open and shut down the burners. Poor airflow, dirty filters, or a failing blower motor often cause overheating.

Recommended Action: Replace or clean air filters, inspect blower motor operation, and ensure vents are unobstructed. Replace the high limit switch if necessary.

Additional Rheem Furnace Diagnostic Lights and Troubleshooting Tips

6+ Blinks and Continuous Flashing

Some Rheem models may use six or more blinks or a continuous flashing light to indicate other specific issues, such as communication errors or sensor failures. Referencing the furnace’s manual is critical for accurate diagnosis.

Resetting the Furnace After Troubleshooting

After resolving the cause of an error code, the furnace control board typically requires a reset. Most Rheem models reset automatically after power cycling, or a reset button may be available on the control board.

Warning: Avoid frequent resets without fixing underlying issues, as this may damage furnace components and pose safety risks.

When to Call a Professional HVAC Technician

If troubleshooting light codes involves complex electrical components, gas valves, or persistent errors despite corrective actions, it’s crucial to engage a licensed HVAC professional. Certified technicians have specialized tools and training to safely diagnose and repair Rheem furnace problems.

Preventive Maintenance to Minimize Furnace Errors

• Regular Filter Replacement: Changing air filters every 1-3 months prevents poor airflow-related errors.
• Annual Inspections: Scheduling professional maintenance ensures sensors, ignitors, and vents are clean and functional.
• Keep Vents Clear: Ensuring indoor and outdoor vents are free of debris supports proper combustion air supply.
• Clean Flame Sensors and Burners: A clean burner area reduces ignition problems and flame sensing errors.

Summary Table of Rheem Furnace Light Codes and Actions

Light Code	Error Explanation	Probable Cause	Suggested Action
1 Blink	Pressure Switch Open	Blocked vent, damaged tubing	Clear vents, replace tubing if damaged
2 Blinks	Pressure Switch Closed	Faulty switch or wiring	Test switch, repair wiring
3 Blinks	Ignition Lockout	No gas, bad ignitor	Check gas supply, inspect ignitor
4 Blinks	Flame Sensor Failure	Dirty/defective sensor	Clean or replace sensor
5 Blinks	High Limit Open	Overheating, airflow restriction	Replace filter, check blower