How to Reset a Furnace: Safe Steps, Troubleshooting, and Pro Tips

A furnace that suddenly quits can be frustrating, especially on a cold night. This guide explains how to reset a furnace safely, what the reset actually does, and how to troubleshoot common issues. It covers gas, electric, and oil models, with clear steps for “how do I reset my furnace” searches, plus when to call a professional.

What Resetting A Furnace Actually Does

Resetting a furnace is a way to clear a temporary fault and allow the system to try again. It can restore operation after issues like brief power glitches, airflow restrictions, or short-lived ignition problems.

A reset does not fix the root cause. If a safety switch tripped or a fault returns after a reset, there’s an underlying problem that needs attention. Repeated resets can be unsafe and may damage components.

There are two common resets. A power-cycle reset removes power for a short period to clear the control board’s fault. A manual reset clears a tripped high-limit or rollout switch (if present) or, on oil systems, the primary control lockout.

Safety First

If you smell gas (rotten-egg odor), do not reset. Leave the area, avoid switches or flames, and call your gas utility and 911 from outside. For oil furnaces, if you see smoke, soot, or smell heavy oil fumes, stop and call a pro.

Turn the thermostat to Off before any reset. For electric or gas furnaces, switch off power at the furnace switch or breaker. Wait at least one to five minutes before restoring power to allow capacitors and the control board to discharge.

Do not bypass safety switches. Never tape down or jump a limit or door switch. On oil units, press the red reset button only once. Repeatedly feeding oil without ignition can flood the chamber and cause a dangerous puff-back.

Quick Answer: How To Reset A Furnace

• Set thermostat to Off, then Heat, and raise the setpoint 5°F above room temperature after the reset.
• Shut power to the furnace at the service switch or breaker. For gas, also turn the furnace’s side switch off.
• Wait one to five minutes. For gas furnaces, this waiting period also helps dissipate any unburned gas.
• Restore power and ensure the blower door is seated to engage the door safety switch.
• For oil furnaces only: Press the red reset button on the primary control once. If it trips again, stop and call a technician.
• Observe startup: inducer/blower starts, ignitor glows/sparks, gas valve opens, flame proves, main blower runs.

If the system fails or trips again, follow the type-specific steps below and review the troubleshooting section.

Finding The Furnace Reset Button

Many modern gas furnaces do not have a single “reset button.” Instead, they use automatic lockouts or reset by power cycling. Electric and oil furnaces commonly have a visible manual reset.

Look behind a lower panel on the furnace cabinet for safety switches and control boards. Always cut power before removing panels to avoid shock and to prevent the blower door switch from shutting the unit down during inspection.

Typical Reset Locations By Furnace Type

Reset Instructions By Furnace Type

Gas Furnaces: Natural Gas Or Propane

Most homeowners will use a power-cycle reset. This clears soft lockouts related to ignition retries, pressure switch faults, or brief power issues.

• Turn the thermostat Off. If it’s a smart thermostat, ensure it has battery or C-wire power.
• Shut off furnace power at the service switch or breaker. Wait one to five minutes.
• Check the blower door is properly seated; the door switch must be depressed.
• Change a dirty filter to restore airflow. A clogged filter often trips the high-limit.
• Inspect intake/exhaust PVC pipes outside for snow, leaves, or nests. Clear obstructions.
• Verify the condensate drain is not clogged. Some furnaces have a float switch that locks out when the drain backs up. Empty the trap and flush with warm water and vinegar if safe access is available.
• Restore power and set the thermostat to Heat with a higher setpoint.
• Watch the ignition sequence. Inducer fan should start, followed by ignitor glow or spark, gas valve click, then flame. The blower starts after heat exchanger warms.

If the furnace shuts down with an error code, note the LED blink pattern on the control board and compare it to the code chart inside the blower door. This will point to issues like pressure switch failure, flame sense fault, or limit trip.

Do not repeatedly reset a gas furnace that trips immediately. Check for blocked vents, dirty filters, and water in the condensate line. If problems persist, call a licensed HVAC technician.

Electric Furnaces Or Air Handlers With Heat Strips

Electric units often trip a high-limit switch when airflow is restricted. After cooling, a manual reset can restore operation if the cause has been addressed.

• Power off the air handler at the breaker. Heating elements are high voltage; avoid contact.
• Change the air filter and ensure all supply and return vents are open.
• Open the access panel and locate the small red or black manual reset on the limit switch near the elements. Press once.
• Check the blower fan and belt (if applicable) for operation and cleanliness.
• Close the panel, restore power, and set the thermostat to Heat.

If the limit trips again, there may be a failed blower motor, dirty evaporator coil, undersized ductwork, or faulty sequencer. Stop resetting and schedule service to prevent overheating.

Oil Furnaces

Oil burners lock out via the primary control when flame fails. The red reset button allows one safe retry after correcting a basic issue.

• Confirm oil level in the tank; if near empty, the burner may be starved of fuel.
• Set thermostat to Off and shut power to the furnace. Wait one to five minutes.
• Change a dirty filter and ensure the chimney or vent is clear.
• Restore power, then press the red reset button once on the primary control.
• Observe flame. If it locks out again, stop. Repeated resets can flood the chamber with oil, causing a dangerous puff-back.

Common causes include a sooted nozzle, clogged oil filter, air in the line, or a failed ignition transformer. Contact an oil technician for bleeding the line, cleaning, or component replacement.

Thermostat, Power, And Airflow Checks Before And After A Reset

Many “how do I reset my furnace” situations turn out to be thermostat, power, or airflow issues. These are quick checks that often restore heat without further resets.

• Thermostat mode: Set to Heat with a setpoint above room temperature. For smart stats, confirm Wi‑Fi outages didn’t switch schedules or eco modes.
• Thermostat power: Replace batteries or confirm the C-wire provides constant power. Reseat the thermostat on its wall plate.
• Circuit breakers: Check furnace/air handler and outdoor unit breakers. Reset tripped breakers by switching fully Off, then On.
• Service switch: Ensure the furnace’s wall switch (looks like a light switch) is On.
• Blower door switch: The panel must be fully latched. An open door cuts power to the unit.
• Air filter: Replace if dirty. Restricted airflow causes high-limit trips and overheating.
• Vents and returns: Open all registers; clear furniture or rugs. Verify return grille isn’t blocked.
• Condensate drain: For high-efficiency furnaces, empty and flush the trap. A float switch can lock out heating.

What If There’s No Reset Button? Control Boards And Error Codes

Modern furnaces rely on control boards to manage the ignition sequence and safety checks. When a fault occurs, the board may enter a soft lockout (auto retry after a delay) or a hard lockout (requires power cycle to reset).

Look for a blinking LED on the control board through a sight window or behind the blower door. Inside the panel, manufacturers post a label decoding blink patterns, such as pressure switch open, flame not proven, rollout open, or limit switch open.

A power-cycle reset clears many soft faults, but do not ignore repeated codes. Persistent pressure switch or flame sense errors indicate issues like blocked vents, inducer problems, or a dirty flame sensor that a technician should address.

Troubleshooting Common Reasons A Furnace Needs Reset

Use the symptoms below to pinpoint likely causes. Address simple items first to avoid unnecessary resets or service calls.

When Not To Reset And Who To Call

Stop and call a professional if any of the following are present. Safety outweighs speed when dealing with combustion or high-voltage equipment.

• Gas smell or suspected leak; evacuate and call the utility and emergency services.
• Repeated lockouts immediately after resets, especially on oil furnaces.
• Soot, smoke, or scorch marks near the burner or venting.
• Water leaks inside the furnace cabinet or around the condensate pump.
• Electrical burning odors, hot breaker, or tripping breakers.
• Visible cracks on the heat exchanger or persistent carbon monoxide alarms.

For warranty coverage, contact the installing contractor or the manufacturer’s authorized service network. Provide the model and serial numbers from the data tag, plus any LED error codes observed.

Preventing Future Lockouts And Resets

Most furnace lockouts relate to airflow, ignition, or moisture control. A few routine tasks can prevent many “reset furnace” situations.

• Filter changes: Replace 1-inch filters every 1–3 months; 4–5 inch media every 6–12 months. Avoid overly restrictive filters unless ductwork is sized for them.
• Annual tune-up: A pro should inspect burners, heat exchanger, gas pressure, flame sensor, ignitor, safeties, and condensate systems.
• Condensate maintenance: Flush traps quarterly with warm water and a small amount of white vinegar; keep drains pitched and clear.
• Keep vents clear: After snow or storms, ensure intake and exhaust pipes are unobstructed. Maintain clearances from landscaping and siding.
• Thermostat checks: Update firmware on smart thermostats, verify schedules, and ensure compatibility with the furnace.
• Oil system care: Annual nozzle and filter replacement, combustion tuning, and vacuuming soot by an oil specialist.

Costs And Timing: What To Expect If Service Is Needed

Prices vary by region and brand, but these typical ranges can help plan next steps if a reset does not restore heat.

• Diagnostic visit: $80–$150 during regular hours; $150–$300 after-hours or emergency.
• Ignitor replacement (gas): $150–$400 installed, depending on part and access.
• Flame sensor clean/replace: $80–$200, often included in maintenance.
• Pressure switch or inducer repairs: $200–$700 depending on assembly and labor.
• Control board: $400–$900 installed, model dependent.
• Blower motor: $400–$1,200; ECM motors cost more than PSC types.
• Electric furnace sequencer/limit: $150–$350 installed.
• Oil burner service: $150–$300 for cleaning/tune-up; more for parts or bleeding lines.

Warranty notes: Many furnaces carry 5–10 years on parts if registered, but labor is often 1–2 years. Keep records of installation date and maintenance to support claims.

Frequently Asked Questions

How Do I Reset My Furnace If It Has No Reset Button?

Use a power-cycle reset: set the thermostat to Off, cut power at the furnace switch or breaker for one to five minutes, then restore power and call for Heat. This clears many control board soft lockouts. If the unit immediately faults again, review error codes and airflow issues before trying again.

Where Is The Furnace Reset Button?

On oil furnaces, the red reset is on the burner’s primary control. On electric furnaces, the manual reset is a small red or black button on the high-limit switch near the heating elements. Most gas furnaces rely on power cycling; some have manual reset rollout or limit switches with small buttons near burners.

How Many Times Can I Press The Reset Button?

Press once. On oil systems, never press repeatedly due to puff-back risk. On gas and electric units, one reset is reasonable after fixing an obvious issue like a dirty filter. Multiple resets indicate an unresolved fault and can be unsafe.

How Long Should I Wait After Turning Power Off?

Wait at least one minute; five minutes is safer to discharge the control board and let gas dissipate. For oil lockouts, allow the burner to stop completely before pressing the red button once after power is restored.

Will Resetting Clear An Error Code?

A power cycle often clears a soft lockout. If the underlying issue persists, the code will reappear. For reliable diagnosis, read the LED blink code on the control board and compare it with the chart inside the panel before clearing it.

What If The Furnace Runs, Then Trips Again?

This often points to overheating from poor airflow. Replace the filter, open all vents, and check for blocked returns. If it still trips, the blower could be failing, ducts undersized, or the evaporator coil dirty. Call a professional if resets don’t hold.

Can I Reset A Furnace After A Power Outage?

Yes. Turn the thermostat Off, power down the furnace for a minute, then restore power and call for Heat. Smart thermostats may also need a reboot. If the blower door was disturbed, ensure it latches to engage the safety switch.

Why Does My Furnace Click But Not Ignite?

Clicks indicate relays or gas valve activity. Likely causes include a failed hot surface ignitor, dirty flame sensor, low gas pressure, or a pressure switch issue. Try one reset after checking vents and filters. If no ignition, schedule service to test components safely.

Should I Turn The Gas Valve Off To Reset?

No. Leave the appliance gas valve in the On position during a standard power-cycle reset. Only turn off the gas if instructed by a technician or if you suspect a leak, in which case evacuate and call your gas utility immediately.

My High-Efficiency Furnace Has Water In The Cabinet—What Now?

Shut power off. Empty the condensate trap if accessible, clear blockages, and verify the drain line slopes toward the pump or drain. A full condensate switch will lock out the furnace. After clearing, restore power and test. If water remains, call a pro.

Is Resetting Safe If A Carbon Monoxide Alarm Went Off?

No. Leave the home and call 911 and your utility. Do not reset or operate the furnace until a professional confirms safe operation and resolves the source of CO. Replace CO alarm batteries only after the cause is remedied.

Extra Tips For Better Results After A Reset

• Listen for the sequence: inducer or blower, ignitor glow/spark, gas valve click, flame, then main blower. Knowing the order helps pinpoint failures.
• Keep a photo of the control board’s wiring and LED code chart inside the panel for quick reference.
• Label breakers for the furnace, air handler, and outdoor unit to avoid shutting the wrong circuit.
• Winter prep: Clear snow from sidewall vents and install vent hoods or screens designed for your model to deter animals, without restricting airflow.
• Document resets: Note date, conditions, and codes. This history helps technicians diagnose intermittent issues.

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