Furnace Troubleshooting Checklist for Michigan Homeowners
It's 11 PM on a Tuesday in January. The temperature outside is eight degrees. Your furnace just stopped running, and your house is already cooling off. Before you panic and call for emergency service at triple the normal rate, there's a furnace troubleshooting checklist every Michigan homeowner should know.
We've been fixing furnaces across Macomb County, Oakland County, and St. Clair County for over 35 years. About 30% of the emergency calls we get could have been solved by the homeowner in five minutes. The other 70% need a professional, and knowing the difference saves you time, money, and a cold night waiting for help.
This guide walks you through the exact steps our NATE-certified technicians take when diagnosing a furnace problem. You'll learn what you can safely check yourself, what requires professional tools and training, and when it's time to replace instead of repair.
Safety First: Before You Start
Before you touch anything on your furnace, understand that you're dealing with high-voltage electricity, natural gas or propane, and combustion. These systems are safe when working properly, but dangerous when something goes wrong.
Turn off power to the furnace at the circuit breaker before inspecting anything inside the cabinet. Most furnaces have a dedicated 15 or 20-amp breaker labeled "furnace" or "HVAC." If you're not sure which breaker controls your furnace, turn off the main breaker.
Look for the furnace power switch, usually mounted on the wall near the unit. It looks like a standard light switch, often with a red cover plate. Make sure it's in the ON position. Homeowners accidentally flip this switch more often than you'd think, especially in basement furnace rooms where it gets mistaken for a light switch.
Carbon Monoxide Warning: If you smell gas, hear a hissing sound near the furnace, or your carbon monoxide detector is alarming, leave the house immediately and call your gas utility from outside. Do not attempt to troubleshoot. Do not turn anything on or off. Just get out.
Gas furnaces produce carbon monoxide as a byproduct of combustion. When the heat exchanger is intact and the venting system works properly, this CO exits through the flue pipe. When something fails, CO can leak into your home. Every home with a gas furnace needs working CO detectors on every floor.
The 5-Minute Furnace Troubleshooting Checklist
When your furnace isn't working, start with these six checks. They take less than five minutes total and solve about a third of the problems we see on service calls in Metro Detroit.
1. Check Your Thermostat Settings
Set the thermostat to HEAT mode, not AUTO or OFF. Set the temperature at least five degrees above the current room temperature. If you have a programmable thermostat, verify the schedule hasn't accidentally set a lower temperature for this time of day.
Replace the batteries if your thermostat uses them. Low batteries cause erratic behavior, including the furnace not responding to temperature changes. Most thermostats start showing a low-battery warning weeks before they fail, but homeowners often ignore it until the system stops working.
If you have a newer smart thermostat and it's showing "No power from R wire" or similar, the 24-volt transformer in your furnace may have failed. That's a professional repair, covered later in this guide.
2. Inspect the Air Filter
Pull out the air filter and hold it up to a light. If you can't see light through it, it's restricting airflow enough to cause problems. A completely clogged filter makes the furnace work harder, overheat, and shut down on the limit switch.
Filters are located either in a slot on the furnace itself or in a return air grille on a wall or ceiling. Standard 1-inch filters should be replaced every 30-60 days during heating season in Michigan. Thicker 4-inch or 5-inch media filters last 6-12 months.
We see this constantly in Sterling Heights and Warren: homeowners who haven't changed their filter in six months wonder why their furnace keeps shutting off. The blower motor is running, but no air moves through the system because the filter is packed solid with dust, pet hair, and debris.
Our Next Care Plan includes filter changes during seasonal tune-ups, but between visits you should check monthly and replace when needed.
3. Verify the Circuit Breaker
Go to your electrical panel and look for the furnace breaker. It should be in the ON position, fully to the right. If it's tripped, it will be in the middle position or all the way to the left. Reset it by pushing it fully to OFF, then back to ON.
If the breaker trips again immediately or within a few minutes, you have an electrical problem that needs professional diagnosis. Don't keep resetting it. A breaker that trips repeatedly is protecting your home from an electrical fault, possibly a failing blower motor or a short in the control board.
4. Check the Furnace Power Switch
That innocent-looking light switch on the wall near your furnace controls power to the entire system. It's required by code so technicians can safely work on the unit. It's also frequently switched off by accident.
Make sure it's in the ON position. If someone was in your basement or utility room recently, they may have bumped it. This is especially common in homes where the furnace is in a storage area or near the laundry.
5. Inspect the Gas Valve (Gas Furnaces)
Follow the gas line to where it enters your furnace. There's a valve with a handle that looks like a small lever. When the handle is parallel to the pipe, the valve is open. When perpendicular (90 degrees), it's closed.
If the valve is closed, someone turned it off. Open it by rotating the handle to align with the pipe. If you recently had work done on your furnace or gas line, the technician may have closed it and forgotten to reopen it.
6. Check the Condensate Drain
High-efficiency furnaces (90% AFUE and above) produce condensation as part of the combustion process. This water drains through a plastic tube into a floor drain, condensate pump, or utility sink.
If that drain line clogs, water backs up into a safety pan. When the pan fills, a float switch shuts down the furnace to prevent water damage. Look for standing water in the drain pan or around the base of the furnace.
You can often clear a clogged condensate line yourself using a wet/dry vacuum on the drain outlet. If water keeps backing up, the drain line may be frozen (common in Michigan) or the trap may be clogged with biological growth.
Common Furnace Problems You Can Fix Yourself
If you've worked through the checklist above and identified the problem, here's what you can safely fix without calling for professional furnace repair services.
Dirty Filter Causing Airflow Restriction
Replace the filter with one that matches the size printed on the old filter's cardboard frame. Don't buy the cheapest filter at the hardware store. Spend a few extra dollars for a MERV 8 or MERV 11 pleated filter. It captures more particles without restricting airflow like the ultra-high MERV 13+ filters do.
Make sure the arrow on the filter frame points toward the furnace (in the direction of airflow). Installing it backward reduces efficiency and can damage the blower motor over time.
Thermostat Programming Errors
If your furnace runs but the house stays cold, check the thermostat schedule. Many programmable thermostats come with default schedules that assume you're away during the day. If you work from home or have irregular hours, those defaults waste energy or leave you uncomfortable.
Set the thermostat to HOLD or PERMANENT HOLD mode to override the schedule temporarily. Then reprogram it to match your actual routine. If your thermostat is not reaching the set temperature even with the schedule corrected, you have a bigger problem.
Tripped Breaker or Blown Fuse
If resetting the breaker once gets your furnace running and it doesn't trip again, you likely had a temporary power surge or the blower motor drew extra current during startup. This happens occasionally and isn't cause for concern.
Older furnaces may have fuses in addition to the circuit breaker. These are usually 3-amp or 5-amp glass tube fuses located in a small holder on the control board. If the fuse is blown (the metal filament inside is broken or the glass is blackened), replace it with an exact match. Keep spares on hand during winter.
Pilot Light Issues (Older Furnaces)
Standing pilot furnaces manufactured before the mid-1990s have a small flame that burns continuously. If this pilot goes out, the furnace won't ignite. You can relight it yourself following the instructions printed on the furnace or in the owner's manual.
The process usually involves turning the gas valve to PILOT, holding down the pilot button, and using a long lighter to ignite the pilot flame. Hold the button for 30-60 seconds after the pilot lights, then release it. The pilot should stay lit. Turn the valve back to ON.
If the pilot won't stay lit, the thermocouple (a safety device that senses the pilot flame) may have failed. That's a $150-200 repair including the service call. Given that these furnaces are 25+ years old at this point, replacement usually makes more sense than repair.
Furnace Problems That Need a Professional
These issues require diagnostic tools, technical knowledge, and often specialized parts. Attempting to fix them yourself risks injury, property damage, and voiding your equipment warranty.
Ignition System Failures
Modern furnaces use electronic ignition instead of standing pilots. Hot surface igniters glow red-hot to light the gas. Spark igniters create a spark like a gas grill. When these components fail, the furnace goes through its startup sequence but never ignites.
You'll hear the inducer motor start, then a clicking sound as the igniter tries to light the gas, then everything shuts down. This cycle repeats several times before the control board locks out and displays a fault code.
Hot surface igniters are fragile silicon carbide or silicon nitride elements that crack from thermal stress or physical contact. They cost $30-60 for the part, but you need a multimeter to verify the igniter is actually the problem and not the flame sensor, gas valve, or control board.
Our techs see this constantly in Troy and Rochester Hills: homeowners who replaced the igniter themselves but the furnace still doesn't work because the actual problem was a dirty flame sensor or a control board that wasn't sending voltage to the igniter.
Cracked Heat Exchanger
The heat exchanger is the metal chamber where combustion happens. Air from your home blows across the outside of the heat exchanger to warm up, while combustion gases flow through the inside and exit through the flue.
When the heat exchanger cracks, combustion gases (including carbon monoxide) can leak into the air circulating through your home. This is dangerous. A cracked heat exchanger means the furnace must be replaced immediately.
You cannot see most heat exchanger cracks without disassembling the furnace and using a video inspection camera. Warning signs include: sooting around the burners, yellow or wavering flames instead of steady blue flames, water pooling inside the furnace, or your CO detector alarming.
Heat exchangers crack from thermal stress (repeated heating and cooling cycles), corrosion (from condensation or flue gas), or long-term operation with restricted airflow (dirty filters). They're more common in furnaces that are 15+ years old.
A heat exchanger replacement costs more than a new furnace in most cases. The labor alone is 8-12 hours because you essentially disassemble the entire furnace. When we find a cracked heat exchanger, we walk homeowners through their replacement options instead of repair.
Blower Motor Problems
The blower motor moves air through your ductwork. When it fails, you'll hear the furnace ignite and run, but little or no air comes out of the vents. Sometimes the motor hums but doesn't spin. Other times it makes grinding or squealing noises.
Blower motors fail from worn bearings, capacitor failure, or electrical problems. The capacitor (a small cylindrical component that helps the motor start) is often the culprit. Capacitors cost $20-40 for the part, but diagnosing which component failed requires testing equipment.
Replacing a blower motor assembly costs $400-800 depending on the furnace brand and motor type. Variable-speed ECM (electronically commutated motor) blowers cost more than single-speed PSC (permanent split capacitor) motors but run more efficiently and quietly.
Limit Switch Failures
The limit switch is a safety device that monitors the temperature inside the furnace. If the furnace overheats (usually from restricted airflow), the limit switch shuts off the burners. The blower keeps running to cool things down.
When a limit switch fails in the open position, the furnace won't ignite because the control board thinks the furnace is already too hot. When it fails in the closed position, the furnace can overheat without shutting down, which is dangerous.
Limit switches fail from age, thermal stress, or repeated cycling caused by dirty filters or blocked ducts. Replacing one costs $150-250 including the service call. But if your furnace is overheating frequently, you have an airflow problem that needs to be fixed or the new limit switch will fail too.
Gas Valve Issues
The gas valve controls gas flow to the burners. It opens when the control board signals for heat and closes when the thermostat is satisfied. When a gas valve fails, you'll hear the inducer motor and see the igniter glow, but no gas flows to the burners.
Gas valves rarely fail on newer furnaces. When they do fail on older systems, it's usually because the valve coil (the electromagnetic component that opens and closes the valve) has burned out. Testing requires a multimeter to check for voltage at the valve and resistance across the coil.
Gas valve replacement costs $300-500 including parts and labor. On furnaces that are 15+ years old, this repair triggers the "replace vs. repair" conversation because you're putting $500 into a system that may have other components fail soon.
What Michigan Winters Do to Furnaces
Michigan winters are hard on heating systems. We see specific failure patterns that correlate directly with weather events.
During polar vortex events when temperatures drop below zero for days, furnaces run almost continuously. Systems that are undersized for the home or losing efficiency from age can't keep up. Homeowners call us saying the furnace runs constantly but the house won't get above 62 degrees.
That's not always a furnace problem. If your home has poor insulation, air leaks around windows and doors, or undersized ductwork, no furnace can overcome the heat loss when it's five below outside. We do load calculations to determine whether you need a bigger furnace or better insulation.
High-efficiency furnaces that vent through PVC pipe instead of metal flue pipe can have their exhaust freeze shut during extreme cold. The furnace shuts down on a pressure switch error because combustion gases can't exit. We see this in Shelby Township and Clinton Township when temperatures stay below 10 degrees for multiple days.
The fix is clearing the ice blockage from the vent termination outside and possibly insulating the vent pipe where it exits the house. Some installations need a vertical vent extension to prevent wind-driven snow from entering the pipe and melting, then refreezing.
Power outages from ice storms shut down your furnace even if you have gas heat. The blower motor, ignition system, and control board all need electricity. If you lose power frequently, consider a backup generator sized to run your furnace, refrigerator, and a few lights.
Humidity from heating creates condensation in ductwork and on furnace components. This is worse in homes with humidifiers that are set too high. We see rust on heat exchangers, mold growth in ducts, and water damage around furnaces in basements that stay too humid all winter.
Keep indoor humidity between 30-40% during winter. Higher than that and you risk condensation on windows, mold growth, and accelerated corrosion of metal components. Lower than 30% and you'll have dry skin, static electricity, and respiratory irritation.
When to Replace Instead of Repair
The decision to repair or replace a furnace comes down to age, repair cost, and efficiency.
Furnaces last 15-20 years on average in Michigan. By year 15, you've gotten your money's worth. Components start failing more frequently. Efficiency drops as heat exchangers corrode and blower motors wear. Parts become harder to find for older models.
Use the 50% rule: if the repair costs more than 50% of what a new furnace would cost, and your furnace is over 12 years old, replace it. A $1,200 repair on a 16-year-old furnace means you'll likely face another major repair within two years. You're better off putting that money toward new equipment.
Modern furnaces are dramatically more efficient than models from 2005-2010. A 95% AFUE furnace converts 95 cents of every dollar spent on gas into heat for your home. An old 80% AFUE furnace wastes 20 cents of every dollar up the flue.
On a typical Michigan heating season where you spend $1,200 on gas, upgrading from 80% to 95% efficiency saves about $225 per year. Over a 15-year furnace lifespan, that's $3,375 in savings, which more than pays for the efficiency upgrade.
New furnaces also qualify for utility rebates and federal tax credits. DTE Energy and Consumers Energy both offer rebates for high-efficiency furnace installations. The federal Inflation Reduction Act provides tax credits up to $2,000 for qualifying ENERGY STAR equipment.
When we diagnose a major repair on an aging furnace, we give homeowners both options: repair cost and replacement cost with financing terms. Our reliable HVAC contractors never pressure you toward the more expensive option. We explain the math and let you decide what makes sense for your situation.
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NEXT Heating & Cooling has been keeping Michigan homes comfortable for over 35 years. Get honest diagnostics and fair pricing from NATE-certified technicians who show up on time.
Schedule Your ServiceFrequently Asked Questions
Change standard 1-inch filters every 30-60 days during heating season (October through April). Check monthly and replace when you can't see light through the filter. Homes with pets, smokers, or people with allergies should change filters every 30 days. Thicker 4-inch or 5-inch media filters last 6-12 months but should still be inspected quarterly.
This is called short-cycling and has several causes. A dirty filter restricts airflow, causing the furnace to overheat and shut down on the limit switch. A failing flame sensor thinks the burners aren't lit and shuts off the gas valve. An oversized furnace heats the space too quickly and cycles frequently. A malfunctioning thermostat sends erratic signals. Start with the filter, then call for professional diagnosis if the problem persists. Our guide on furnace short-cycling causes covers this in detail.
A dusty or burning smell when you first turn on the furnace in fall is normal. Dust accumulated on the heat exchanger over summer burns off during the first few heating cycles. This smell should disappear within a few hours. If you smell gas (rotten eggs), shut off the gas valve, leave the house, and call your gas utility. If you smell burning plastic or electrical smoke, turn off the furnace at the breaker and call for service immediately.
Service call fees range from $89-150 depending on the company and time of day. Simple repairs like replacing a filter, thermostat batteries, or resetting a tripped breaker may only cost the service call. Component replacements range from $150-300 for small parts (flame sensor, limit switch, capacitor) to $400-800 for major components (blower motor, gas valve, control board). Emergency service after hours or on weekends costs 1.5-2x normal rates. Our detailed breakdown of furnace service call costs in Metro Detroit covers current 2026 pricing.
No. A furnace leaking water indicates a problem that will get worse if you keep running it. High-efficiency furnaces produce condensation that drains through a tube. If that tube is clogged or frozen, water backs up and can damage the heat exchanger, control board, and blower motor. The furnace may have a safety switch that shuts it down when water accumulates, but if that switch fails, you risk water damage to your home. Turn off the furnace and call for service. Learn more about why furnaces leak water and what it means.
Yes. Annual maintenance prevents 80% of furnace breakdowns and extends equipment life by 5-10 years. Our Next Care Plan costs $5/month ($60/year) and includes two annual visits: a fall furnace tune-up before heating season and a spring AC tune-up before cooling season. You also get priority scheduling, 10% off repairs, and no service call fees. A single emergency repair during a polar vortex event can cost more than five years of maintenance.
We install and service all major brands including Carrier, Lennox, Trane, Rheem, Bryant, Goodman, Amana, York, and RUUD. For Michigan's climate, we typically recommend mid-to-high efficiency models (92-96% AFUE) from Carrier, Lennox, or Trane for homeowners who want premium reliability, and Rheem or Bryant for those prioritizing value. The most important factors are proper sizing (load calculation), correct installation, and regular maintenance. A properly installed mid-tier furnace will outlast a premium model that was poorly installed. Our York furnace repair guide covers one popular brand in detail.