Rheem Furnace Error Codes Guide: Troubleshooting, Meanings, and Fixes

Rheem furnace error codes help diagnose issues quickly and guide safe, efficient repairs. This guide explains common Rheem error codes, what they mean, likely causes, and practical troubleshooting steps homeowners and technicians can use to restore heating performance. Safety first: power off the unit before inspecting components beyond basic checks.

Code	Typical Meaning	Quick Action
PSI/1 Blink	Pressure Switch Or Venting Issue	Check vent blockage, hose, and switch continuity
2 Blink	Ignition Or Flame Sense Problem	Inspect ignitor, flame sensor, and gas supply
3 Blink	Open High Limit Or Overheat	Check airflow, filter, blower, and limit switch
4 Blink	Flame Failure Or Lockout	Reset after checking gas valve and flame path

How Rheem Displays Error Codes

Rheem furnaces typically display error codes through a control board LED that blinks in a repeating pattern or shows an alphanumeric code on an electronic interface. Understanding the blink pattern sequence is essential to map the blink count to the correct fault description in the service manual.

In some models, the control board also provides status LEDs for power, call for heat, and diagnostic outputs. Always consult the model-specific installation and service manual for exact LED behavior and code definitions.

Common Rheem Furnace Error Codes And Meanings

Pressure Switch Fault (1 Blink)

The pressure switch confirms proper venting and inducer operation before ignition. A 1-blink code usually indicates the switch failed to close or open as expected.

Possible causes include blocked venting, failed inducer motor, cracked or disconnected pressure tubing, or a faulty pressure switch. Technicians often measure vacuum at the tubing and test switch continuity to confirm the failure.

Ignition Or Flame Sense Fault (2 Blink)

A 2-blink code points to unsuccessful ignition or inability to detect flame. This can result from a weak or cracked hot surface ignitor, a dirty or degraded flame sensor, gas valve issues, or improper gas pressure.

Common fixes include cleaning the flame sensor with fine emery cloth, testing ignitor resistance and watching ignition sequence, and inspecting the gas valve coil for correct operation and voltage.

Open High Limit Or Overheat (3 Blink)

When the furnace overheats or the high limit switch opens, a 3-blink code usually appears. Restricted airflow is the most frequent cause, often due to a clogged filter, blocked return, faulty blower motor, or closed duct dampers.

Technicians should check filter condition, blower wheel, airflow across the heat exchanger, and measure the limit switch for continuity when cool. Also verify the duct system and blower speed settings.

Flame Failure Or System Lockout (4 Blink)

A 4-blink code typically signals repeated flame failures leading to a lockout. This could be caused by intermittent gas supply, valve issues, or an erratic flame sense circuit.

Resetting the unit may restore operation temporarily, but recurrent lockouts require diagnosing the gas train, flame sensor signal integrity, and error history for intermittent faults.

Less Common Codes And Specialized Faults

Com-Pump Or Control Board Communication Errors

Some Rheem furnaces that include communicating components or multiple boards can log communication errors when modules fail to handshake. Symptoms include no ignition and diagnostic LEDs indicating a bus fault.

Verify wiring harness connections, inspect for water damage or corrosion on connectors, and replace the control board if communication cannot be restored.

Limit Switch And Sequencer Failures

Multiple trips of the limit switch or sequencer faults suggest chronic overheating or a defective control component. Recurrent trips damage system reliability and often mask underlying airflow problems.

Corrective work should prioritize restoring proper airflow, validating fan operation, and replacing any limit switches that do not reset to spec.

Inducer Motor And Venting Faults

Inducer motor problems cause the system to halt before ignition. Symptoms include loud or unusual inducer noise, failure to reach appropriate vacuum on the pressure switch, or motor not spinning.

Inspect vent terminations for obstructions (bird nests, debris), measure voltage to the inducer motor, and confirm impeller integrity and motor bearings.

Step-By-Step Troubleshooting Workflow

The following workflow helps isolate and address common Rheem furnace error codes safely and efficiently.

1. Turn Off Power: Cut power at the furnace or breaker before inspection beyond visual checks.
2. Record Code And Behavior: Note the blink pattern, display code, and any unusual sounds or smells.
3. Visual Inspection: Look for loose wires, burnt connectors, blocked vents, or water leaks.
4. Check Airflow: Replace the air filter and verify blower operation and return grilles are unobstructed.
5. Test Safety Switches: With power off, test pressure and limit switches for proper continuity and vacuum response.
6. Inspect Ignition Components: Verify ignitor resistance, clean or replace the flame sensor, and inspect gas valve solenoids.
7. Reset And Monitor: Restore power and observe the startup sequence and code behavior for changes.

When To Call A Professional

Some repairs require licensed HVAC technicians, especially those involving gas components, refrigeration, or sealed combustion systems. Call a professional when there is a suspected gas leak, repeated ignition lockouts, control board replacement needs, or if the homeowner lacks the tools or confidence for electrical testing.

Safety reminder: Never attempt gas valve or combustion adjustments without the correct certification, tools, and procedures. Improper handling can result in carbon monoxide risk or fire.

Maintenance Tips To Prevent Future Error Codes

Regular maintenance reduces the risk of Rheem furnace error codes and improves system longevity and efficiency.

• Replace Filters: Change disposable filters every 1–3 months depending on use and indoor air quality.
• Annual Tune-Up: Schedule yearly professional inspections to test combustion, controls, heat exchanger integrity, and gas pressure.
• Keep Vents Clear: Maintain clear intake and exhaust terminations outside and ensure attic or crawlspace vent runs are unobstructed.
• Clean Flame Sensor: Clean the flame sensor annually to prevent false flame failure codes.
• Monitor Thermostat Wiring: Ensure thermostats are properly wired and batteries replaced regularly to avoid intermittent calls for heat.

Model-Specific Notes And Resources

Rheem produces multiple furnace families—Classic, Prestige, and Professional—each with model-specific diagnostics. The blink codes and digital display messages can vary by control board generation.

For accurate diagnosis, reference the model and serial number on the furnace data plate and download the exact service manual from Rheem’s official website or authorized distributor portals.

Example Troubleshooting Cases

Case: 2-Blink Ignition Failure After Power Surge

Situation: A homeowner reports a 2-blink code after a recent power outage and surge. The furnace attempted to ignite but locked out. Inspection found a cracked hot surface ignitor and a charred control board terminal.

Action: Replace the ignitor and repair control board connections. Add a surge protector for the furnace power leg to reduce future electronic damage.

Case: 3-Blink Overheat In A Home With New Insulation

Situation: After attic insulation upgrades, the furnace began tripping high limit switches with a 3-blink code. Restricted return airflow and increased house tightness were noted.

Action: Adjust return grille sizes, clean and replace the filter, and install a variable-speed blower configuration or increase duct return capacity to improve airflow and reduce limit trips.

Parts And Tools For DIY Diagnosis

Homeowners comfortable with basic HVAC tasks can perform non-gas, non-electrical-disconnect checks with a few tools and parts on hand.

• Multimeter for voltage and continuity checks
• Small pocket mirror and flashlight for visual inspection
• Fine emery cloth for flame sensor cleaning
• Replacement air filters and a basic tool kit
• Manufacturer replacement parts like ignitors or pressure switches when specified

For anything involving gas valves, regulators, or sealed combustion adjustments, a licensed technician is required.

How To Read The Control Board LED Blink Patterns

To decode a blink pattern, observe the LED for a full cycle and count the number of blinks followed by a pause. Many Rheem boards flash the error count repeatedly with a pause between sequences.

Document the count and the interval, then consult the model’s service sheet. Some boards also include secondary LEDs that indicate stage of operation which can help isolate the fault to pre-ignition, ignition, or flame sensing stages.

Resources And Official Documentation

For accurate, up-to-date information, consult these authoritative sources: Rheem product manuals, Rheem technical service bulletins, and HVAC trade resources like the Air Conditioning Contractors Of America (ACCA) for safe practices.

Owner manuals and service guides include wiring diagrams, error code tables, and step-by-step startup procedures specific to each furnace model. These documents are the definitive reference for proper troubleshooting and repairs.

Key Takeaways For Homeowners And Technicians

Recognize patterns: Error codes typically correlate to pre-ignition checks, ignition/flame sensing, or safety trips. Accurate observation and documentation accelerate repairs.

Prioritize safety: Power down before inspections, avoid DIY gas adjustments, and contact licensed professionals for combustion or gas-related issues.

Regular maintenance prevents many faults: Clean flame sensors, replace filters, and verify venting to reduce common errors and extend furnace life.