Furnace Exhaust Buried in Snow Cleared but No Heat: Troubleshooting Steps

When A Furnace Exhaust Vent Was Buried In Snow And Has Been Cleared But There Is Still No Heat, Several Safety Devices And System Faults Could Be Preventing Operation. This Guide Explains Practical Troubleshooting Steps, Safety Checks, And When To Call A Professional To Restore Heat Safely.

Quick Checklist	Action
Safety First	Check Carbon Monoxide Alarm And Ventilation
Power & Controls	Verify Thermostat, Breaker, Switches
Reset Sequence	Reset Furnace Power/Control Board
Drain & Switches	Clear Condensate Lines And Check Float Switch
Professional Help	Call HVAC If Fault Codes Or Persistent No Heat

Why A Buried Exhaust Can Stop A Furnace

High-efficiency furnaces Rely On Exhaust Venting And Fresh-Air Intake To Operate Safely. When A Vent Is Buried In Snow, The System Can Become Blocked, Causing Pressure To Rise And Safety Switches To Open.

Common Effects Include Furnace Shutoff, Tripped Pressure Or Blockage Switches, Condensate Backups, And Potential Carbon Monoxide Risks If The Unit Tries To Run With Improper Venting.

Immediate Safety Steps

If The Exhaust Was Buried, Begin By Ensuring The Home Is Safe. Turn Off The Furnace If There Is Any Suspicion Of Improper Combustion Or A Persistent Gas Smell.

Check Carbon Monoxide (CO) Alarms And Replace Batteries Or Units If They Are Old. Evacuate If CO Alarms Are Active Or If Anyone Feels Dizziness, Headache, Or Nausea.

Check Power, Thermostat, And Basic Controls

Verify That The Furnace Has Power: Check The Circuit Breaker, A Dedicated Switch Near The Unit, And Any GFCI Outlets That May Control It. Reset A Tripped Breaker Before Further Troubleshooting.

Confirm The Thermostat Is Set To Heat And The Setpoint Is Higher Than Room Temperature. Replace Thermostat Batteries If Applicable. A misconfigured thermostat is an easy but common cause of “no heat.”

Inspect The Exhaust Vent And Intake

Physically Inspect The Exhaust Termination Outside. Ensure The Vent Cap Is Clear Of Snow, Ice, Debris, And That The Exhaust Path Is Open. Clear Any Remaining Obstruction Carefully.

Also Check The Fresh-Air Intake (If Remote). Some High-Efficiency Units Use Sidewall Intake Chambers That Can Be Blocked Separately From The Exhaust.

Reset The Furnace Control Board

After Clearing The Vent, Turn Off Power To The Furnace For 30 Seconds And Then Restore It. Many Furnaces Require A Power Reset To Clear Faults And Retry The Startup Sequence.

If The Furnace Displays A Fault Code Or Flashing LED After Reset, Note The Pattern. Fault Codes Provide Clues Such As Pressure Switch Failure, Ignition Failure, Or Limit Switch Trips.

Condensate Drain And Float Switch Issues

High-efficiency Condensing Furnaces Produce Water That Drains Through A Condensate System. When The Exterior Vent Is Buried, Condensate Can Back Up And Reach A Float Switch Or Safety Switch That Prevents Operation.

Check The Condensate Drain Trap And Line For Ice Or Blockage. Clear Or Thaw The Line Gently; use warm (not boiling) water or a wet/dry vacuum to remove obstructions.

Pressure Switch And Venting Sensors

The Furnace Uses A Pressure Switch To Confirm Proper Draft Before Ignition. If The Vent Was Blocked, The Pressure Switch May Have Failed Or Stuck Open. After Clearing The Vent, the switch may remain tripped until the furnace is cycled properly.

Pressure Switch Problems Can Be Caused By A Collapsed Or Ice-Clogged PVC Vent, Loose Tubing To The Switch, Or Internal Switch Failure. Visual inspection and listening for the inducer motor are helpful diagnostics.

Inducer Motor And Exhaust Fan Checks

The Inducer Motor Creates Draft Through The Heat Exchanger Before Ignition. If This Motor Fails Or If Its Startup Is Interrupted By A Safety Fault, The Furnace Won’t Ignite.

Listen For The Inducer Running During A Startup Attempt. If It Runs Then Stops, Count LED Fault Flashes And Reference The Manufacturer’s Code Chart Or The Furnace Manual.

Ignition And Flame Sensing

Even After Clearing A Vent, The Furnace May Fail To Ignite If The Ignitor, Gas Valve, Or Flame Sensor Is Faulty. A malfunctioning flame sensor can cause the unit to try to light repeatedly then lock out.

Flame sensors Often Need Cleaning; however, tight or repeated lockouts indicate a deeper gas or control issue requiring a technician.

Common Fault Codes And What They Mean

Many Furnaces Use LED Flash Codes On The Control Board. Typical Indicators Include: 1 Flash (Normal), 2–3 Flashes (Pressure Switch), 4 Flashes (Ignition Failure), 5–6 Flashes (Flame Loss Or Limit Trips). Consult The Unit’s Manual For Accurate Interpretation.

Write Down The Exact Flash Pattern And The Furnace Model When Calling For Service; This Saves Time And Helps The Technician Diagnose Remotely.

Troubleshooting Sequence To Try At Home

1. Ensure Safety: Check CO Alarm And Vent Clearance.
2. Confirm Power: Reset Breaker And Furnace Switch.
3. Thermostat: Verify Settings And Batteries.
4. Reset Furnace: Turn Off Power 30 Seconds, Restore.
5. Observe Startup: Listen For Inducer Motor And Note Fault Codes.
6. Check Condensate: Clear Drain Lines And Float Switch.
7. Re-inspect Vent: Ensure No Ice Or Debris Remains.
8. If Still No Heat: Document Fault Codes And Call A Licensed HVAC Tech.

When To Consider Calling An HVAC Professional

If The Furnace Still Won’t Run After Basic Checks, If Fault Codes Persist, Or If The Unit Cycles Erratically, A Professional Is Recommended. Also Call Immediately If CO Alarms Are Active Or If There’s A Strong Gas Odor.

Qualified Technicians Will Perform Pressure Tests, Inspect The Heat Exchanger For Damage, Measure Gas Pressure, And Replace Faulty Sensors Or Controls Safely.

Emergency Situations And Carbon Monoxide Risks

A Blocked Exhaust Increases The Risk Of Combustion Products Entering The Home. Because CO Is Odorless And Dangerous, any suspicion of improper venting requires immediate attention.

Evacuate If CO Alarms Activate, Ventilate The Home If Safe To Do So, And Call Emergency Services For Medical Symptoms Or If Gas Leaks Are Detected.

Preventive Measures To Avoid Future Blockages

Keep The Area Around Sidewall Vents Clear Of Snow, Ice, And Debris. Create A Regular Snow Removal Routine During Heavy Snowfalls To Prevent Reburial.

Install A Vent Deflector Or Raise The Termination Height If Local Codes Allow, And Consider A Remote Intake Location If Wind-Driven Drifts Are Common.

Maintenance Checklist After A Snow Event

• Inspect And Clear Exhaust Termination Every Few Hours During Heavy Snow.
• Check Condensate Lines For Ice; Insulate Or Heat Tape If Prone To Freezing.
• Test CO Detectors And Replace Batteries Annually.
• Schedule Annual HVAC Maintenance To Ensure Proper Operation And Reliable Safety Device Function.

Cost Considerations For Repairs

Simple Repairs Like Clearing A Condensate Line Or Resetting A Furnace May Be Low-Cost Or DIY. Replacement Of Pressure Switches, Inducer Motors, Or Control Boards Can Range From Moderate To Higher Costs Depending On Parts And Labor.

Emergency Service Calls During Cold Spells May Carry Premiums. Obtain An Estimate And Ask About Warranties On Repaired Parts.

What To Tell The Technician For Faster Service

Provide The Furnace Make, Model, Serial Number, Exact Fault LED Pattern If Any, A Description Of The Vent Blockage Event, And Any Actions Already Taken. This Helps Technicians Bring Parts And Plan Necessary Tests.

Long-Term Solutions For Cold Climates

Consider Upgrading To A Unit With Higher Vent Termination Or A Longer Intake/Exhaust Location If Snow Drifts Are Regularly Problematic. Professional Site Assessment Can Recommend Changes To Reduce Future Blockages.

Adding External Heated Condensate Lines Or Insulating Vulnerable Components Can Also Improve Reliability In Freezing Conditions.

Resources And Manufacturer Guidance

Consult The Furnace Owner’s Manual For Specific Error Codes, Reset Procedures, And Safety Notices. Manufacturer Websites Often Provide Troubleshooting Guides And Videos For Common Faults.

Local Utility Companies Or HVAC Associations May Offer Emergency Repair Lists And Safety Information About Carbon Monoxide And Heating System Operation.

Key Takeaways

Clear The Vent Safely, Prioritize Carbon Monoxide Safety, Check Power And Thermostat, Reset The Furnace, Inspect Condensate And Pressure Switches, And Call A Professional If Faults Persist. Prompt Action Reduces Risk And Restores Heat Faster.