Rheem Furnace Error Code 13: Meaning, Causes, and Troubleshooting

The Rheem Furnace Error Code 13 signals a specific fault that requires targeted troubleshooting to restore safe heating operation. This article explains what Code 13 means, common causes, step-by-step diagnostics, safety precautions, likely parts to inspect, estimated repair costs, and maintenance tips to reduce recurrence. The guidance applies to Rheem and similarly designed Ruud furnaces used in U.S. homes.

Item	Quick Summary
Error Code	Rheem Furnace Code 13 (Ignition Failure/Trial For Ignition Fault)
Common Causes	Ignitor failure, gas valve, flame sensor, blocked burners, wiring, control board issues
Immediate Action	Power cycle, check gas supply, inspect error LED & control board label, call pro if unsure
When To Call A Pro	Persistent Code 13 after basic checks, smell of gas, or no furnace heat

What Rheem Furnace Code 13 Means

Rheem Furnace Code 13 typically indicates an ignition failure or a trial-for-ignition limit reached where the furnace attempted to light but did not detect a confirmed flame within the allowed cycles. Different Rheem/Ruud control boards may label codes slightly differently, but Code 13 generally points to ignition or flame-detection problems.

How The Furnace Ignition Sequence Works

Understanding the ignition sequence clarifies why Code 13 occurs. The thermostat calls for heat; the inducer motor runs; pressure switch confirms venting; the ignitor activates; the gas valve opens; flame must be sensed within a set time; the burner stays on while flame sensor verifies continuous flame.

If flame is not detected during the allowed time or is lost immediately after ignition, the control board will lock out and display an error such as Code 13 to protect the system and home safety.

Common Causes Of Rheem Furnace Code 13

• Failed Ignitor: A cracked or electrically open hot surface ignitor (HSI) will not light the burners.
• Faulty Gas Valve or Low Gas Pressure: The gas valve may not open or gas pressure may be insufficient to support ignition.
• Dirty Or Misaligned Flame Sensor: A coated sensor may not register flame even when burners light.
• Blocked Burners Or Orifices: Debris, spider webs, or dust can prevent proper gas flow and flame formation.
• Pressure Switch Or Inducer Issues: If the inducer or pressure switch fails, the sequence may not reach ignition or may abort early.
• Control Board Or Wiring Faults: Loose, corroded, or damaged wiring and defective control modules can produce false Code 13 errors.
• Venting Problems: Restricted exhaust or intake can cause poor combustion and failure to establish a stable flame.

Initial Safety Checks Before Troubleshooting

Safety first. Turn off power to the furnace at the service switch or breaker before opening access panels. If there is a smell of gas, leave the area immediately, evacuate occupants, and call the gas utility or 911. Do not attempt repairs if the operator lacks experience with gas appliances.

Step-By-Step Troubleshooting For Code 13

1. Verify The Error Code And Status LED

Check the control board LED flash pattern or digital display and consult the furnace’s service manual. Confirm the error is Code 13 and note whether it’s intermittent or persistent.

2. Power Cycle The Furnace

Resetting the furnace can clear transient faults. Turn off power for 60 seconds and restore. If Code 13 returns within a few cycles, further diagnosis is required.

3. Check Thermostat And Calls For Heat

Ensure the thermostat is set correctly and is actually calling for heat. A wiring short or incorrect setting could create confusing symptoms.

4. Inspect The Ignitor

Visually inspect the ignitor. For hot surface ignitors, look for cracks. Test continuity with a multimeter if access and skill permit. A failed ignitor often results in immediate Code 13 on each trial.

5. Examine The Flame Sensor

Remove the flame sensor and gently clean it with fine steel wool or emery cloth to remove oxidation and deposits. Reinstall and test; a dirty sensor is a common and easily fixed cause.

6. Check Burners And Orifices

Inspect burners for rust, spider webs, or debris. Clean with a brush and compressed air. Ensure burners seat correctly and gas orifices are unobstructed.

7. Verify Gas Supply And Valve Operation

Confirm other gas appliances operate normally. Check the furnace gas shutoff valve is open. If the gas valve does not respond or gas pressure is low, contact the gas utility or a licensed technician.

8. Inspect Inducer Motor And Pressure Switch

Ensure the inducer runs smoothly and the pressure switch tubing is clear. A stuck inducer or failed pressure switch can abort ignition attempts.

9. Check Wiring And Ground Connections

Look for loose, burnt, or corroded wires at ignitor, flame sensor, control board, and gas valve. Poor grounds or shared neutrals can create intermittent Code 13 faults.

10. Evaluate The Control Board

If all components test good, the control board or its relays may be malfunctioning. Boards can be bench-tested by professionals; replacement is sometimes necessary when logic or sensing circuits fail.

Diagnostic Tools And Tests

• Multimeter for continuity and voltage checks.
• Manometer for measuring gas pressure.
• Combustion analyzer for proper flame characteristics (used by technicians).
• Inspection mirror, flashlight, small brush, and compressed air for cleaning burners and sensors.

Parts Most Likely To Be Replaced

Common replacement parts for resolving Code 13 include the hot surface ignitor, flame sensor, gas valve, pressure switch, inducer motor, and occasionally the control board. The precise part depends on diagnostics.

Estimated Repair Costs

Repair costs vary by region and complexity. Typical ranges: ignitor $150–$350 (parts and labor), flame sensor $80–$200, gas valve $300–$700, inducer motor $200–$600, control board $250–$900. Exact pricing requires an on-site diagnosis.

When To Call A Professional

• After basic checks (reset, inspect ignitor/sensor, clean burners) if Code 13 persists.
• If there is any gas smell or suspected leak.
• If wiring, gas valve, or control board replacement is needed.
• When safe operation or combustion testing is required.

Licensed HVAC technicians have the tools and certification to safely handle gas valves, combustion analysis, and control board troubleshooting.

Preventative Maintenance To Avoid Code 13

• Schedule annual professional tune-ups before heating season.
• Keep furnace area free of dust and debris and change filters regularly.
• Clean burners and flame sensor annually or as recommended.
• Ensure proper venting and condensate drainage to prevent pressure or safety switch issues.

Differences Between Rheem And Ruud Codes

Rheem and Ruud share many design elements and sometimes identical control boards. Code numbering may vary slightly by model, so consult the unit-specific service manual. When in doubt, reference the label on the control board or the installer manual for the exact meaning of Code 13 for that model.

Frequently Asked Questions About Rheem Furnace Code 13

Is Code 13 Dangerous?

Code 13 itself is a protective lockout indicating ignition failure. The code helps prevent unsafe operation. The situation is not inherently dangerous if the furnace powers down, but any gas odor or malfunction requires immediate attention.

Will Resetting The Furnace Fix Code 13 Permanently?

Resetting can clear transient faults but will not fix underlying hardware failures. Reoccurring Code 13 indicates a component problem that needs inspection.

Can Homeowners Replace The Ignitor Or Flame Sensor?

Residents with mechanical aptitude and correct parts can replace ignitors or flame sensors, following safety guidelines and power disconnection. Those uncomfortable with gas appliances should hire a licensed technician.

How Long Can A Furnace Run With Code 13 Present?

Most furnaces will lock out and stop heating after repeated failed ignition attempts. Continued operation is unlikely until the fault is corrected.

Resources And Manuals

Locate the furnace model number on the furnace data plate to download the specific Rheem or Ruud service manual from the manufacturer website. Manuals include control board LED code charts and wiring diagrams essential for accurate troubleshooting.

Additional reliable resources include the Rheem/Ruud technical support lines, HVAC professional organizations, and licensed local contractors who provide diagnostic services.

Key Takeaways

• Rheem Furnace Code 13 generally indicates ignition or flame-sensing failure.
• Start with safe, basic checks: power cycle, inspect and clean the flame sensor and burners, confirm gas supply.
• If issues persist, call a licensed HVAC technician to test the gas valve, ignitor, inducer, pressure switch, and control board.

For persistent Code 13 issues or any sign of gas leakage, prioritize safety and contact a professional immediately. Proper diagnosis prevents wasted parts replacement and ensures safe, reliable heating performance.