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A Rheem furnace pilot light is a small but essential flame that initiates and sustains combustion in a gas furnace. While many modern Rheem models use electronic ignition, older systems rely on a standing or intermittent pilot to light the burner. This guide explains how a Rheem furnace pilot light works, common problems, safe relighting steps, and practical maintenance tips to keep heating reliable through cold months. Readers will learn to diagnose simple issues and decide when professional service is appropriate.

What Is a Pilot Light and How It Works in Rheem Furnaces

The pilot light is a small flame that continuously burns in some Rheem gas furnaces. In standing-pilot systems, the flame heats a thermocouple, generating a small electrical current that keeps the gas valve open. If the flame goes out, the thermocouple cools and the valve closes, stopping gas flow for safety. In modern Rheem units with intermittent pilots or electronic ignition, a sensor or ignition module replaces the continuous flame, firing the burner when heat is needed.

Two key components govern operation: the thermocouple, which produces millivolts to hold the gas valve open, and the thermopile or ignition module in newer designs, which replaces or augments the traditional thermocouple. A clean, properly adjusted flame ensures efficient combustion and reduces soot and CO risks. Understanding these parts helps homeowners interpret symptoms like flame instability or repeated ignition attempts.

Types Of Rheem Furnace Ignition

Rheem furnaces may use a standing pilot, an intermittent pilot, or a hot-surface ignition (HSI) system. A standing pilot burns continuously and requires manual relighting if the flame goes out. An intermittent pilot lights only when heat is requested, using an electronic spark or hot surface to ignite the main burner. HSI systems rely on a high-temperature element to ignite the burner without a standing pilot. Identifying your model’s ignition type is essential before attempting any maintenance or relighting.

Older Rheem models often display a visible flame at the pilot assembly and require periodic inspection of the pilot tube and orifice. Newer models with electronic ignition may not have a visible pilot flame and rely on sensors and a control board to start the burner. Model labels, owner manuals, and Rheem’s support resources are good references for confirming the ignition type and recommended service intervals.

Common Symptoms When The Pilot Light Fails

• Pilot light won’t ignite after relighting attempts.
• Pilot flame goes out shortly after ignition.
• Burner fails to stay lit or the furnace frequently shuts off.
• Flame is yellow, flickering, or weak, indicating incomplete combustion.
• Gas odor or hissing sound near the furnace, which requires immediate action.
• Frequent resets or fault codes on the furnace control board related to ignition.

Noting the flame color and stability can help diagnose issues: a healthy blue flame indicates proper combustion, while a yellow or orange flame may signal dirt, insufficient air, or fuel-supply problems. If a gas odor is detected, evacuate and contact emergency services.

Step-By-Step Guide To Relighting A Rheem Pilot Light

1. Turn off the thermostat and set the furnace gas control to Off. If a pull tab or emergency shutoff is present, use it to disable gas flow.
2. Wait 5–10 minutes to clear any accumulated gas. This minimizes the risk of a flashback or explosion.
3. Access the pilot assembly. Locate the gas control knob or switch labeled Pilot, On, and Off. In some models, you may need to remove a furnace access panel.
4. Turn the knob to Pilot (or the appropriate pilot setting) and press and hold the reset/ignition button if present.
5. While holding, use a long lighter or the built-in ignition tool to light the pilot. Continue holding for 30–60 seconds after the flame appears to heat the thermocouple.
6. Release the knob and turn the control to On or Run. The burner should ignite when heat is required. If the flame is unstable or goes out, repeat once or consult a professional.
7. Close the access panel and restore the thermostat to its previous setting. Observe the furnace for a few minutes to ensure stable operation.

Note: Some Rheem models with electronic ignition do not have a standing pilot. In these cases, relighting procedures differ and may require using the ignition switch or restarting the furnace from the control panel. If relighting fails or you cannot locate the pilot components, contact a licensed HVAC technician.

Safety Precautions And When To Call A Pro

• If you smell gas at any time, evacuate the area and call emergency services or your gas utility immediately.
• Do not attempt to repair fuel components beyond relighting procedures. Gas valves, thermocouples, and ignition modules are safety-critical.
• Keep the furnace area clear of flammable materials and ensure proper ventilation and a working CO detector in the home.
• If the pilot won’t stay lit after relighting, or you hear continuous gas flow when the valve should be off, discontinue use and seek professional service promptly.
• For Rheem furnaces with electronic ignition or complex fault codes, professional diagnostics help prevent improper gas combustion and potential safety hazards.

Maintenance Tips To Prevent Pilot Light Problems

• Schedule annual professional inspections to verify gas pressure, venting, and burner alignment. A tune-up can prevent pilot-related failures.
• Inspect and clean the pilot orifice and burner ports. A dirty or clogged orifice can cause weak or unstable flames.
• Replace a failing thermocouple or thermopile. Worn sensors reduce the ability to hold the gas valve open, causing ignition problems.
• Ensure proper venting and adequate combustion air. Obstructions or restricted vents can lead to incomplete combustion and flame instability.
• Check the gas supply line for leaks or pressure issues. Inconsistent gas pressure can prevent reliable ignition and flame stability.
• Test detectors for carbon monoxide and maintain safety devices. Regular checks reduce the risk of CO exposure from improper combustion.

Common Causes Of Pilot Light Problems In Rheem Furnaces

The following table links typical components to common symptoms and practical remedies: