Rheem Furnace Pilot Light: Troubleshooting, Reset Steps, and Safety Tips

A pilot light problem can halt a home’s heat on the coldest night. This guide explains how a Rheem furnace pilot system works, how to safely relight it, and what to do if it keeps going out. It covers both older standing-pilot models and newer Rheem furnaces that use spark or hot-surface ignition. With safety-first steps, practical troubleshooting, and clear maintenance advice, homeowners can restore reliable heat—or know when to call a professional.

How Rheem Furnace Pilot Systems Work

Rheem has produced gas furnaces with several ignition styles. Some older models use a standing pilot that burns continuously. Others use intermittent pilot ignition, where a spark lights a small pilot only during a heat cycle. Many modern Rheem furnaces use a hot surface ignitor to light burners directly without a pilot.

Standing Pilot vs. Electronic Ignition

A standing pilot has a small flame that stays on. A thermocouple sits in this flame, generating a tiny electrical signal that keeps the gas valve open. If the flame goes out, the signal drops and gas flow stops for safety. An intermittent pilot uses a spark to light a pilot when the thermostat calls for heat, then opens the main gas valve. A hot surface ignitor glows red-hot to light the burners—no pilot flame is present.

Key Components In Pilot-Based Systems

Pilot Burner/Orifice: A small jet where the pilot flame emerges; can clog with debris.
Thermocouple/Thermopile: Senses the flame’s heat and generates millivolts to keep the safety valve open.
Gas Control Valve: Has Off/Pilot/On positions on standing-pilot units; electronically controlled on newer models.
Flame Sensor (Electronic Ignition): Detects flame via microamp current after ignition; dirty sensors cause shutdowns.
Safety Switches: Limit and rollout switches prevent unsafe operation from overheating or flame rollout.

How The Safety Circuit Protects Your Home

The gas valve will not allow main burner operation unless flame is proven. On standing pilots, a thermocouple provides a small DC voltage (typically 25–35 mV under load) to hold the valve open. On electronic systems, the control board must see flame via a flame sensor or it will immediately close the gas valve and lock out after multiple failed attempts.

Quick Identification: Does Your Rheem Have A Pilot Light?

Look for a “Pilot” knob: Remove the burner compartment door. If the gas valve has Off/Pilot/On and a push-down button, it’s a standing pilot.
Watch a heat cycle: If you hear a rapid tick-tick spark at startup and see a small flame first, it’s an intermittent pilot. If a ceramic stick glows red and burners light without a small pilot, it’s a hot surface ignitor.
Check the inside door label: Rheem furnaces include a lighting instruction sticker listing ignition type and steps.
Model family clues: Many legacy Rheem/Ruud models used pilots; high-efficiency models (condensing with PVC venting) almost always use electronic ignition.

Safety Checklist Before You Relight

If you smell gas: Do not relight. Do not use switches or phones inside. Leave immediately and call your gas utility or 911 from outside.
Ventilation matters: Propane is heavier than air and can pool low; natural gas is lighter and rises. Any gas odor is an emergency.
Shut off power: Switch off furnace power at the service switch or breaker to prevent unexpected operation during checks.
Have the right tools: Long-reach lighter or match, flashlight, and a small brush or compressed air for light cleaning.
Allow time: If gas was recently turned off, air may be in the line; it can take longer to establish a steady pilot.

How To Relight A Rheem Furnace Pilot Light (Standing Pilot)

Use the specific instructions on your furnace’s door sticker if available. The steps below reflect common Rheem standing-pilot procedures.

Step-By-Step Relight Guide

Set the thermostat to Off or its lowest setting and turn off furnace power at the switch.
Access the pilot assembly by removing the burner compartment door for clear visibility.
Turn the gas control knob to Off and wait at least 5 minutes to clear any residual gas. If you still smell gas after waiting, evacuate and call your utility.
Locate the pilot burner and thermocouple. Identify where the pilot flame should appear and where the small metal tip of the thermocouple sits.
Turn the gas control knob to Pilot. Press and hold the knob or pilot button to start gas flow to the pilot.
Light the pilot with a long-reach lighter or match while continuing to hold the button. The pilot flame should ignite immediately.
Hold the button down 30–60 seconds to heat the thermocouple. Stronger heating helps the safety valve stay engaged.
Release the button slowly. The pilot should remain lit. If it goes out, repeat once more, holding longer (up to 90 seconds) to compensate for air in the line.
Turn the gas knob to On. Restore power and set the thermostat to call for heat.
Observe burner ignition. Burners should ignite smoothly with a steady blue flame.

What A Proper Pilot Flame Looks Like

Color: Mostly blue with a small yellow tip is normal; a lazy, yellow, lifting, or noisy flame suggests an issue.
Shape/Contact: The flame should envelop the top 3/8–1/2 inch of the thermocouple. Poor contact will cause dropouts.
Stability: The flame should be steady, not flickering or blowing off the tip.

Post-Relight Checks

Watch a full cycle: Ensure the blower starts, the burner remains stable, and the furnace shuts off normally.
Check for drafts: Strong drafts can blow out the pilot; address air leaks or door gaps in the furnace room.
Replace the door: Many Rheem furnaces have a door switch that must be engaged for operation.

If The Pilot Won’t Stay Lit

Repeated pilot outages point to fuel, flame quality, or sensor issues. The table below outlines common symptoms and actions.

Symptom	Likely Cause	DIY Checks	Next Step
Pilot lights but goes out when button released	Cool thermocouple, misaligned flame, weak thermocouple	Hold longer to heat; adjust pilot flame contact; gently clean tip	Replace thermocouple if problem persists
Pilot won’t light at all	No gas to pilot, clogged orifice, gas shutoff closed	Confirm gas supply and valve position; inspect for debris	Have a pro clear orifice or check valve
Pilot lights but main burners don’t	Insufficient thermocouple signal, faulty gas valve, limit open	Confirm strong blue pilot; ensure blower door switch engaged	Technician testing of millivolts and controls required
Pilot goes out intermittently	Drafts, cracked heat exchanger affecting draft, dirty pilot	Seal drafts; clean pilot area carefully	HVAC inspection for venting or exchanger faults
Yellow, sooty pilot	Restricted air, improper gas pressure	Lightly clean pilot intake	Pro adjustment to manifold pressure and combustion

Thermocouple Basics And Replacement

A thermocouple generates a small voltage when heated by the pilot. Under load, a healthy unit typically produces about 25–35 mV. If it is weak, the gas valve drops out and the pilot won’t stay lit. Thermocouples are inexpensive and often standardized, but the length and mounting style must match the furnace.

Signs of failure: Pilot holds only while pressing the button; goes out upon release despite a strong flame.
Cleaning: Lightly buff the thermocouple tip with fine abrasive. Do not bend or kink the capillary tube.
Replacement: Shut off gas and power, allow cooling, then remove the old unit and install the new one hand-tight plus a gentle snug. Check for leaks with a soap solution after reassembly.

Intermittent Pilot And Hot Surface Ignition: Reset And Troubleshooting

Many newer Rheem furnaces do not have a standing pilot. They rely on electronic controls that lock out after failed ignition attempts. The following steps help restore operation safely.

General Reset Steps (Electronic Ignition)

Set the thermostat to Off and turn off furnace power for 60 seconds.
Restore power and call for heat. Watch through the sight glass for the ignition sequence.
Note any LED flash codes on the control board visible through the blower door window. The inside door sticker explains code meanings.
Verify air filter condition and that all registers are open; poor airflow can trigger limits and lockouts.

If You Have An Intermittent Pilot (Spark Ignition)

Spark but no pilot flame: Gas to pilot may be off or the pilot orifice could be clogged. A technician can clean the orifice and verify gas pressure and spark gap.
Pilot lights but burners don’t: The control may not be sensing flame. A flame-sense rod may need gentle cleaning with fine abrasive.
No spark sound: Suspect ignition module, ground, or wiring. Have a pro test for safe operation.

If You Have A Hot Surface Ignitor (No Pilot)

Ignitor glows but no flame: Gas valve, pressure, or a stuck closed valve is possible. Call a professional for live-fire diagnostics.
Ignitor never glows: The ignitor may be cracked. Do not touch the element with bare hands. Replacement is common but should be verified with proper testing.
Flame starts then shuts off: A dirty flame sensor is common. Lightly clean the sensor rod; reassemble securely and ensure a good ground.

Seasonal Maintenance For Reliable Ignition

Annually: Have a licensed HVAC technician perform combustion analysis, inspect heat exchanger, clean burners, and verify gas pressure and safety switches.
Before heating season: Gently clean the pilot assembly and surrounding area, check venting for obstructions, and ensure the condensate system (if present) is clear.
Every 1–3 months: Replace or clean furnace filters to maintain airflow and prevent limit trips that can interrupt ignition cycles.
Carbon monoxide safety: Install CO alarms outside sleeping areas and on each level of the home. Test monthly and replace per manufacturer guidance.

Common Rheem-Specific Notes

Rheem and Ruud are sister brands: Many parts and procedures are interchangeable; manuals for either often apply.
Door switch interlock: Rheem furnaces typically have a door switch. The unit will not operate with the door removed.
Control board diagnostics: Rheem furnaces display LED codes. The exact meanings are printed on the blower door label—always consult this chart.
High-efficiency models: Condensing Rheem furnaces use PVC venting and do not have a standing pilot. They require electronic ignition troubleshooting.

When To Call A Professional

You smell gas at any point.
Repeated pilot failures despite a strong, blue flame and a new thermocouple.
Rollout switch trips or scorch marks near burners—potential flame rollout or heat exchanger issues.
Venting concerns, downdrafts, or soot anywhere in the furnace or vent pipe.
Electrical faults such as tripped breakers, blown fuses on the control board, or persistent error codes.
Any adjustment to gas pressure or conversion between natural gas and propane—these require licensed service and proper orifices.

FAQs: Rheem Furnace Pilot Light

Does Every Rheem Furnace Have A Pilot Light?

No. Many modern Rheem furnaces use hot surface ignition with no pilot. Some have intermittent pilot ignition. Only older models typically have a standing pilot light.

How Long Should I Hold The Pilot Button?

Usually 30–60 seconds is sufficient to heat the thermocouple. After gas service interruptions or if air is in the line, holding up to 90 seconds can help establish a stable pilot.

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What If The Pilot Flame Is Yellow?

A mostly yellow flame indicates poor combustion or restricted air. Light cleaning of the pilot intake may help, but gas pressure or combustion adjustments must be done by a professional.

Can I Bypass A Faulty Thermocouple?

No. Bypassing any safety device is dangerous and illegal. Replace the thermocouple or have the system serviced.

Where Is The Reset Button On A Rheem Furnace?

There is no universal “reset” button for ignition. For electronic models, power cycling and addressing fault codes is the correct approach. Some rollout switches have a manual reset button but should not be repeatedly reset without fixing the cause.

How Do I Know If I Have A Bad Gas Valve?

Professional testing compares thermocouple output and valve requirements, checks manifold pressure, and verifies proper operation. DIY replacement is discouraged due to leak and combustion risks.

Is Keeping A Standing Pilot Lit Expensive?

Standing pilots consume a small but continuous amount of gas. While the cost is modest, modern electronic ignition furnaces are more efficient overall and reduce fuel use.

Parts, Tools, And Typical Costs

Item	Purpose	Typical Price (Parts)	Notes
Thermocouple	Holds gas valve open when heated	$10–$25	Match length and mounting style
Flame Sensor	Proves burner flame on electronic units	$15–$40	Clean before replacing
Hot Surface Ignitor	Lights burners (no pilot)	$30–$90	Fragile; avoid touching element
Ignition Control Module	Controls spark and sequencing	$100–$300	Diagnosis required
Gas Valve	Controls gas flow	$150–$400	Install and leak-check by a pro
Pilot Assembly	Includes pilot burner and orifice	$40–$120	Cleaning may restore function

Labor costs vary by region. Simple cleaning or a thermocouple replacement may cost $125–$250. Electronic ignition diagnostics and parts can range $200–$600 or more depending on complexity.

Energy And Safety Upgrades

CO Detection: Install listed carbon monoxide alarms on each level and near bedrooms. Replace per manufacturer schedule.
Sealed Combustion Furnaces: Upgrading from a standing-pilot furnace to a modern high-efficiency Rheem with sealed combustion and electronic ignition improves safety and reduces fuel consumption.
Smart Thermostats: Maintaining even temperatures reduces short cycling that can stress ignition components.
Venting Improvements: Correct vent sizing, clearances, and slope mitigate downdrafts that can blow out pilots.

Troubleshooting Flow: From No Heat To Heat

Confirm power and thermostat settings. Replace thermostat batteries if applicable.
Check the furnace switch and breaker. Ensure the blower door is properly installed to engage the door switch.
Look for error codes. Reference the Rheem door label for diagnostic guidance.
For standing pilots: Relight using safe procedure. Observe flame quality and thermocouple contact.
For electronic ignition: Reset power, watch the sequence, and clean the flame sensor if the flame lights then drops out.
If issues persist: Schedule professional service to test gas pressure, sensor signals, and safety controls.

Glossary

Standing Pilot: A continuously burning flame used to ignite burners.
Intermittent Pilot: A pilot that lights only during a call for heat via spark.
Hot Surface Ignitor: A ceramic element that ignites gas without a pilot.
Thermocouple: Flame-heated sensor generating millivolts to keep the gas valve open.
Flame Sensor: Rod that confirms flame to the control board via microamp current.
Rollout Switch: Safety device that trips if flame leaves the burner area.
Limit Switch: Opens on high temperature to prevent overheating.

Sources And Further Reading

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