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

Rheem furnace fault codes help identify operational problems quickly and accurately. This guide explains common Rheem furnace fault codes, how to read and interpret them, step-by-step troubleshooting, basic fixes, and when to contact a licensed HVAC technician. Readers will learn safety-first diagnostic steps and preventive maintenance tips to reduce repeat errors and extend equipment life.

Code	Symptom	Likely Cause
1 Flash	Thermostat call or normal operation	Normal/No fault
2 Flashes	Pressure switch stuck open	Blocked venting, bad switch
3 Flashes	Ignition lockout	Ignitor failure, gas valve, flame sensor
4 Flashes	Flame sensed when not calling	Flame rectification issue, wiring
5 Flashes	No flame detected	Ignitor, gas supply, flame sensor dirty

How Rheem Furnace Fault Codes Work

Rheem furnaces use an LED or control board to display fault codes, typically as a sequence of flashes. The number and pattern correspond to specific diagnostic categories. Understanding the code sequence and associated LED behavior is the first step in accurate diagnosis.

The control board monitors components such as the pressure switch, ignition system, flame sensor, blower motor, and limit switches. When a monitored parameter falls outside expected norms, the board logs a fault and communicates it via the LED code and sometimes via a diagnostic port or app on Wi‑Fi enabled models.

Reading The LED And Control Board

Most Rheem furnaces present codes through a green or red LED. The board will flash a pattern: a pause followed by a number of fast flashes, then repeat. Consult the unit’s data plate or owner’s manual for the exact code table because patterns vary by model family.

To read codes accurately, observe the flame or status LED for at least one full cycle. Count the number of flashes between pauses. Some models indicate continuous steady lights for certain statuses; cross-reference with the manual to avoid misinterpretation.

Common Rheem Furnace Fault Codes And Meanings

The following list covers frequently encountered Rheem furnace fault codes and typical causes. Variations can exist by model, so use these as guidance rather than absolute rules.

1 Flash — Normal Operation

One flash typically indicates normal operation when the system is running. No action is required if the furnace operates normally and there are no heat complaints.

2 Flashes — Pressure Switch Open Or Inducer Issues

Two flashes often point to an open pressure switch, blocked venting, failed inducer motor, or loose pressure tubing. Symptoms include delayed ignition or repeated attempts to light.

Checks: Inspect vent and intake for obstructions, verify inducer runs on call, and ensure pressure switch tubing is secure and not collapsed.

3 Flashes — Ignition Lockout

Three flashes typically indicate the control has entered ignition lockout after multiple failed ignition attempts. Common causes are a weak or failed ignitor, clogged burners, or gas valve issues.

Checks: Observe ignitor glow sequence, confirm gas supply and valve operation, and inspect burner flame pattern when possible.

4 Flashes — Flame Detected When Not Intended

Four flashes often mean the control senses flame outside a normal call for heat. This can result from electrical noise, flame rectification leakage, or wiring faults between the flame sensor and control board.

Checks: Inspect flame sensor mounting and wiring, clean sensor with fine emery cloth, and verify proper grounding of the furnace chassis.

5 Flashes — No Flame Detected

Five flashes indicate the control did not sense flame during the ignition sequence. Causes include dirty or failing flame sensor, bad ignitor, interrupted gas flow, or wiring issues.

Checks: Clean flame sensor, confirm ignitor operation, verify gas line and pilot/gas valve operation, and check error history for intermittent faults.

6 Flashes — Limit Or High Temperature Cutout

Six flashes point to a high-limit trip or overheating condition. This can be caused by restricted airflow, dirty filters, blower failure, or blocked return ducts.

Checks: Replace or clean air filters, ensure proper blower operation, inspect heat exchanger airflow and venting for restrictions, and measure static pressure if available.

7+ Flashes — Miscellaneous And Board-Specific Codes

Seven or more flashes often correspond to model-specific errors such as communication faults, RPM feedback problems, or low-line voltage. These require model-specific diagnostics using the manual or service tools.

Checks: Review the unit’s manual code chart and consider logging codes with a multimeter or HVAC diagnostic tool for intermittent electrical issues.

Step-By-Step Troubleshooting Process

Follow a systematic approach to resolve Rheem furnace fault codes safely and efficiently. Always shut power off before handling internal components and follow local codes and safety practices.

1. Record The Code: Write down the exact LED sequence and any observed behavior such as repeated tries to ignite.
2. Visual Inspection: Check for obvious issues — loose wires, burned connectors, blocked vents, or water in condensate traps.
3. Check Filters And Airflow: Replace dirty filters and clear return vents to restore proper airflow.
4. Verify Power And Gas: Ensure the furnace switch is on, breakers are closed, and gas supply is open.
5. Test Ignition Sequence: Observe inducer, pressure switch operation, ignitor glow, gas valve opening, and flame establishment.
6. Clean Flame Sensor: Remove and gently clean the flame sensor with fine emery cloth or steel wool; reinstall securely.
7. Inspect Venting And Condensate: Ensure PVC vent lines and condensate traps are clear and pitched correctly.
8. Reset And Retest: After addressing causes, reset power or use the reset button; monitor for reoccurrence of the fault code.

Basic Fixes Homeowners Can Safely Perform

Several common problems are safe for a homeowner to address. If the homeowner is unsure or the fix requires gas or complex electrical work, contact a licensed technician.

• Replace Or Clean Air Filters: Improves airflow and reduces limit trips.
• Clear Vents And Intakes: Remove debris or bird nests obstructing the intake/exhaust.
• Clean Flame Sensor: Use gentle abrasion to remove oxidation for reliable flame detection.
• Reset Furnace Power: Turn off power for 30 seconds to reset control boards and clear transient faults.
• Check Thermostat Settings And Wiring: Confirm proper call for heat and secure thermostat wires.

When To Call A Professional

Contact a licensed HVAC technician when faults involve gas valves, heat exchanger cracks, persistent ignition lockouts, control board replacement, or complex electrical diagnostics. Safety and local code compliance require professional service for many repairs.

Symptoms that warrant immediate professional help include the smell of gas, repeated limit trips, visible cracks in the heat exchanger, or persistent flame failure after basic homeowner checks.

Preventive Maintenance To Reduce Rheem Furnace Fault Codes

Regular maintenance reduces the frequency of fault codes and improves furnace longevity. Annual or biannual tune-ups by a qualified technician are recommended, especially before heating season.

• Annual Inspection: Professional check of burners, heat exchanger, ignitor, flame sensor, and combustion efficiency.
• Quarterly Filter Changes: Replace or clean HVAC filters every 1–3 months depending on usage and pets.
• Keep Vents Clear: Maintain at least one foot clearance around intake/exhaust terminations.
• Service Condensate System: For high-efficiency Rheem furnaces, ensure condensate traps and PVC drains are clear.
• Test Safety Devices: Confirm limit switches, rollout switches, and pressure switches operate properly.

Model-Specific Considerations And Resources

Rheem furnaces include different control boards and code sets across model families, including Classic, Prestige, and EcoNet-enabled units. Always consult the unit’s installation or service manual for exact fault code definitions and troubleshooting diagrams.

Rheem provides online resources such as product manuals, wiring diagrams, and technical bulletins. Official Rheem Support and certified dealer manuals are reliable references for accurate code interpretation and wiring schematics.

Common Misdiagnoses And How To Avoid Them

Misreading codes or ignoring environmental factors can lead to incorrect repairs. For instance, cleaning a flame sensor may temporarily clear a code while the real issue remains a failing gas valve or intermittent wiring fault.

To avoid misdiagnosis: combine code reading with observation of sequence behavior, use proper tools (multimeter, manometer), and refer to model-specific documentation before replacing major components.

FAQ — Quick Answers About Rheem Furnace Fault Codes

How Often Do Rheem Furnaces Display Fault Codes?

Fault codes appear whenever the control detects a parameter outside normal ranges. Intermittent issues may cause occasional codes while persistent malfunctions produce continuous or repeating codes.

Can A Furnace Code Be Cleared Without Fixing The Problem?

Resetting power can clear stored codes temporarily but will not fix underlying mechanical or electrical faults. Persistent issues will reappear and should be investigated.

Is It Safe To Run The Furnace With A Fault Code Displayed?

Some codes indicate non-critical statuses, but anything related to flame failure, gas, or overheating should be treated as potentially hazardous. Stop operation and investigate or call a professional if unsure.

Where Is The Fault Code LED Located?

The LED is usually on the control board behind the furnace access panel or on the exterior control box. Refer to the manual or data plate for the exact location relative to the model number.

Tools And Equipment Useful For Diagnostics

Common tools for diagnosing Rheem furnace fault codes include a digital multimeter, clamp ammeter, manometer (for combustion/pressure checks), basic hand tools, and an HVAC thermometer. For electronics-level diagnostics, a service technician may use flame rectification meters and combustion analyzers.

Tool	Purpose
Multimeter	Verify voltage, continuity, and sensor signals
Manometer	Test pressure switch and venting differential
Clamp Ammeter	Check inducer and blower motor current draw
Combustion Analyzer	Assess combustion efficiency and CO levels

Final Notes On Safety And Best Practice

Safety is paramount when working on gas-fired equipment. Always shut power and gas when performing component replacement or wiring work and verify zero energy state with appropriate tools. Follow manufacturer’s instructions and local codes, and hire licensed HVAC professionals for gas or heat exchanger repairs.

This guide is intended to provide accurate, actionable information about Rheem furnace fault codes and common troubleshooting steps. For model-specific diagnostics refer to Rheem documentation or consult a certified technician for complex or hazardous issues.