Lennox Furnace Reset Button: Location, Safe Use, and Troubleshooting Guide

A “Lennox furnace reset button” can mean different things depending on the model. Some Lennox units have manual safety resets, while others require a control board reset. This guide explains what counts as a reset button, where to find it, how to use it safely, and what to do if it keeps tripping.

What The Lennox Furnace Reset Button Really Is

Most modern Lennox gas furnaces do not have one big universal “reset” button. Instead, they may have several manual reset safety switches that trip when unsafe conditions occur. Common examples include a flame rollout switch, an auxiliary limit switch, or a blower motor thermal reset.

In many models, “reset” refers to resetting the control board by cycling power or clearing lockout conditions after a fault. Some older oil furnaces do have a prominent red burner reset button, but it must be used with care.

Knowing which type of reset applies to your Lennox furnace helps prevent damage and addresses the cause of the shutdown rather than just restarting it.

Where To Find A Reset Button On Different Lennox Furnaces

Gas Furnaces (Most Common In The U.S.)

Modern Lennox gas furnaces typically include a circuit board with an LED diagnostics light and interlock door switches. They may have manual-reset safety switches if abnormal heat or flame is detected.

• Flame Rollout Switch: Usually near the burners or heat exchanger. Small round device with two wires and a tiny red button in the middle on some models. If tripped, investigate cause before resetting.
• Auxiliary/Manual Reset Limit Switch: May be mounted on the blower housing or heat exchanger area. Not every unit has a manual-reset style; many are automatic reset only.
• Blower Motor Thermal Reset: Some blower motors have a small reset button on the motor housing. If it pops, the motor likely overheated.

There is often no single “master reset” button on Lennox gas furnaces. Resetting typically means power cycling and addressing safety switches.

Oil Furnaces (Less Common, But Important)

Many oil-fired Lennox units use a burner primary control with a red reset button. Press it only once after correcting issues like lack of oil or a tripped limit. Repeated presses can cause dangerous fuel buildup and delayed ignition.

If the oil burner trips again after one reset, stop and call a qualified technician. Do not keep resetting an oil burner.

Electric Air Handlers/Heat Pumps

Lennox electric air handlers may have thermal overloads on blower motors and electric heat sequencers with internal limits. Many limits are automatic reset, while blower motors can include manual reset buttons. There is typically no single furnace “reset button.”

Safety First: When Not To Press The Reset Button

• Smell Gas: Leave immediately, avoid switches and flames, and call your gas utility and 911 from outside.
• Signs Of Flame Rollout Or Scorching: Soot, melted wiring, or burn marks around the burner compartment indicate a serious hazard.
• Repeated Trips: If a limit or rollout switch trips more than once, do not keep resetting. There’s an unresolved fault.
• Oil Burner Lockouts: Only press once. Multiple resets can lead to an explosion hazard.
• Carbon Monoxide Alarm: If a CO detector alerts, ventilate, leave, and call professionals. Do not reset the furnace.

These conditions require diagnosing the cause before attempting to restart the unit.

Step-By-Step: How To Safely Reset A Lennox Furnace

Option A: Simple Control Reset (Gas Furnaces)

1. Set Thermostat To Off: Turn heat off and fan to Auto.
2. Shut Off Power: Use the furnace’s service switch (looks like a light switch) or the dedicated breaker. The blower door switch also cuts power when the panel is removed.
3. Wait 30–60 Seconds: This discharges the control board and relays.
4. Restore Power: Replace the door securely, flip the service switch on, and reset the breaker if needed.
5. Call For Heat: Set thermostat to Heat and raise the setpoint above room temperature.
6. Observe: Watch the ignition sequence (inducer starts, pressure switch proves draft, ignitor glows, gas valve opens, flame stabilizes, blower ramps up). If it faults again, note LED codes.

Option B: Reset A Manual Safety Switch (Gas Furnaces)

1. Power Off First: Always disconnect power at the service switch or breaker.
2. Locate The Switch: Identify a small device with two wires and, if manual-reset, a tiny red button. Common locations are near burners (rollout) or on the blower housing (manual limit).
3. Press Firmly: Press the red button until it clicks. If it does not click, it may not have tripped or it may be an automatic-reset limit.
4. Address The Cause: Check filter, vents, and registers. Look for blocked intake/exhaust, dirty burners, or closed dampers.
5. Restore Power And Test: Reinstall panels, restore power, and call for heat. If the switch trips again, stop and call a pro.

Option C: Oil Burner Primary Control Reset

1. Correct Obvious Issues: Ensure oil tank is not empty and the oil valve is open. Replace a clogged filter only if qualified.
2. Press Reset Once: Press the red reset on the burner control one time only.
3. If It Trips Again: Do not press it repeatedly. Call a licensed oil technician to diagnose ignition, nozzle, pump, or draft issues.

Tools You Might Need

• Flashlight: To see small buttons and labels inside the furnace cabinet.
• Smartphone: For photos and to read the model-specific manual and error codes.
• Vacuum And Brush: To gently clear dust around the cabinet (do not disturb burner or sensor wiring).

If There’s No Reset Button: How To Reset The Control Board

Many Lennox gas furnaces reset by cycling power to the control board. This clears temporary lockouts caused by ignition retries or momentary faults.

• Power Cycle: Turn the furnace service switch off for 30–60 seconds, then back on. Ensure the blower door is fully closed to engage the door switch.
• Thermostat Reset: Set system to Off for a minute, then back to Heat and call for heat.
• Breaker Check: Confirm the furnace breaker and any GFCI outlets on the condensate pump circuit are not tripped.

If lockouts return, the control board is reporting a persistent issue that needs diagnosis.

Interpreting Lennox Error Codes And What They Mean

Lennox furnaces use LED flash codes on the control board. Meanings vary by model, but these are common patterns on many SureLight-style boards. Always confirm with your exact manual.

Locate the LED inside the lower blower compartment. The inside of the panel often includes a sticker with model-specific code definitions.

Why A Reset Tripped: Common Root Causes

• Restricted Airflow: Dirty filters, closed supply registers, blocked return grills, or undersized ductwork can overheat the heat exchanger, opening a limit switch.
• Blocked Vents: Snow, leaves, or nests can block intake or exhaust on high-efficiency units, causing pressure switch faults.
• Dirty Flame Sensor: Oxidation on the sensor rod stops flame signal, leading to repeated ignition attempts and lockout.
• Condensate Drain Issues: On condensing furnaces, a clogged trap or pump can trip a pressure switch or shut down the burner.
• Weak Ignitor Or Low Gas Pressure: Ignition failures trigger retries, then lockout.
• Blower Problems: Failed capacitor, motor overload, or loose belt in older belt-drive systems can cause overheating and limit trips.
• Heat Exchanger Or Flame Rollout: Cracked exchanger or blocked heat path can push flame out of the burner area, tripping rollout safety.
• Electrical Issues: Reversed polarity, poor ground, or intermittent neutral can cause nuisance lockouts.

Quick Troubleshooting Checklist Before You Reset

• Filter: Inspect and replace if dirty. MERV 8–11 balances airflow and filtration in most homes.
• Vents And Registers: Open at least 80% of supply registers. Clear return grills from furniture and dust.
• Outdoor Intake/Exhaust (90%+ AFUE Units): Remove snow, leaves, or insect nests. Ensure terminations are unobstructed.
• Condensate: Check for water in the furnace base, a full condensate pump reservoir, or kinks in the tubing.
• Electrical: Verify the furnace switch is on, breaker is not tripped, and the blower door is seated.
• Thermostat: New batteries if applicable. Confirm mode is Heat and temperature is set higher than room temperature.
• Listen And Observe: Note whether the inducer starts, whether the ignitor glows, and whether the LED flashes a code.

Preventive Maintenance To Avoid Future Resets

• Filter Changes: Replace 1-inch filters every 1–3 months, thicker media every 3–6 months, or as pressure drop dictates.
• Annual Professional Service: Have a licensed technician clean burners, check gas pressure, inspect heat exchanger, verify venting, and test safeties.
• Clean Flame Sensor: A light polish with a non-abrasive pad during service helps maintain reliable flame detection.
• Condensate Care: Clean the trap, flush lines, and test the pump annually on condensing models.
• Vent Clearances: Keep intake/exhaust terminations at least several feet from shrubs and away from drifting snow lines.
• Duct And Blower Health: Inspect blower wheel for dust buildup and ensure proper motor amperage and capacitor health.
• Thermostat And Wiring: Secure low-voltage connections and update old mercury stats to modern digital controls.
• Surge Protection: A whole-home surge protector can help protect sensitive control boards from voltage spikes.

How To Identify Your Specific Lennox Model And Documentation

Look for the nameplate inside the blower compartment or on the side of the cabinet. Record the model and serial number. Use that information to access model-specific literature.

• Lennox Owners Resources provides links to product manuals and maintenance tips.
• LennoxPROs includes technical literature for many models. Some content requires trade access; your contractor can retrieve needed documents.

The installation and operation manual will show exact locations of rollout switches, limit switches, the control board, and LED code definitions for your unit.

Common Reset Locations And What They Mean

When To Call A Professional

• Persistent Lockouts: Repeated LED codes or trips after a single reset attempt indicate a deeper issue.
• Rollout Trips: Any flame rollout event is a serious hazard that requires immediate professional diagnosis.
• Gas Or CO Concerns: Odor of gas, elevated CO readings, or detector alarms demand urgent service.
• Electrical Problems: Tripped breakers, reversed polarity codes, or frequent surges require a technician or electrician.
• Water Leaks: Condensate leaks inside the furnace or on the floor can damage components and cause shutdowns.

Technicians have instruments to measure combustion, static pressure, temperature rise, gas pressure, and electrical values—essential for safe repairs.

Cost And Time Expectations

Costs vary by region and issue severity. Typical ranges include service calls for diagnosis, cleaning flame sensors, replacing pressure switches, or ignitor replacement. Complex issues like heat exchanger cracks, inducer failures, or control board replacements cost more.

Ask for a written estimate and confirm warranty coverage. Many Lennox furnaces carry part warranties, but labor is often separate.

FAQs: Lennox Furnace Reset Button

Does Every Lennox Furnace Have A Reset Button? No. Many gas furnaces rely on control board resets and automatic limits. Manual reset switches are present on some safety devices.

Where Is The Lennox Furnace Reset Button Located? It depends. Look for a red manual-reset button on flame rollout switches or blower motors. Otherwise, resetting means cycling power to the control board.

Is It Safe To Press A Reset Button? Yes, if the cause is minor and corrected, like a clogged filter. Do not repeatedly reset, and never reset if you smell gas or see signs of overheating.

How Many Times Can I Press An Oil Burner Reset? Press once only. Multiple presses can dump oil into the chamber and create an explosion risk.

Will Resetting Erase Error Codes? Power cycling can clear active lockouts. Note the LED code before resetting so a technician can diagnose effectively.

Can A Dirty Flame Sensor Cause Lockouts? Yes. Cleaning the sensor during annual service is a common fix for ignition retries and no-heat calls.

What If The Blower Door Switch Keeps Cutting Power? Ensure the panel is fully seated and latches properly. A misaligned door can prevent operation.

Model-Specific Tips For Popular Lennox Lines

• High-Efficiency EL/SLP Series: Watch for condensate issues and blocked PVC vents. The pressure switch is sensitive to drainage and venting.
• ML/EL Gas Furnaces: Many use SureLight controls with LED codes; the rollout limit may be manual reset. Access the burner compartment with power off to inspect safely.
• Older Oil Models: The red burner reset is on the primary control. Press once and call for service if lockout repeats.

Always consult the exact manual for your model to confirm reset locations and LED code meanings.

Simple Seasonal Checklist To Prevent Reset Events

• Before Heating Season: Replace filter, test thermostat, clear vents, flush condensate trap, and schedule a tune-up.
• Mid-Season: Check filter again, confirm registers are open, listen for unusual noises, and verify no water is present near the furnace.
• After A Storm: Inspect outdoor terminations for snow or debris and verify the furnace intake and exhaust are clear.
• Any Time You Lose Heat: Note the LED code, check the breaker and service switch, and verify the blower door is seated.

Key Takeaways On The Lennox Furnace Reset Button

• No Single Universal Button: In most Lennox gas furnaces, resetting means addressing safety switches and power cycling the control board.
• Manual Resets Are Safety Devices: Flame rollout and some limits have a red reset, but they trip for serious reasons—diagnose the cause.
• Oil Furnaces: The red burner reset is for one press only. Repeated lockouts require professional service.
• Error Codes Are Clues: Use the control board LED to identify likely issues before resetting.
• Prevention Matters: Proper airflow, clean sensors, clear vents, and regular maintenance reduce shutdowns and improve safety.

Helpful Resources

• Lennox Owners Resources for manuals and care tips.
• ENERGY STAR for HVAC maintenance guidance and efficiency tips.
• CPSC Home Heating Safety for general heating safety practices.

If in doubt, prioritize safety. A persistent reset or any evidence of flame rollout, overheating, gas odor, or CO alarm is a clear sign to stop and schedule professional service.