Key Takeaways
- Never forget, though—your safety should always come first, so shut off any power and learn emergency shutoff procedures before attempting to check out your furnace.
- Avoid unnecessary service calls by starting with some simple troubleshooting steps such as checking the thermostat, power switch, circuit breaker and air filter for easy fixes.
- First things first, determine if your furnace is gas or electric. Afterward, complete model-specific troubleshooting steps like relighting the pilot light or fixing error codes.
- Regular filter changes and keeping vents and registers clear can keep your furnace running efficiently all year long.
- Schedule your annual professional tune-ups! Use a seasonal maintenance checklist to avoid expensive repairs and help your system last longer.
- Learn when to end your DIY project! If you ever smell gas, see electrical issues, or have unusually persistent problems, immediately call a professional.
It’s a scenario that millions of Americans—including you—will likely experience at some point in their lives: your furnace won’t turn on. This problem is exacerbated in the winter months. During the severe cold this winter, homeowners may have found their heat still off even after correctly setting their thermostat.
Dead batteries in the thermostat, a tripped breaker, clogged air filters and a shut-off gas valve can keep a furnace from turning on. These are easy things to miss, but don’t skip over them! In warmer cities such as Los Angeles, the weather can render furnaces dormant for months at a time. Because of that, little problems get missed.
Before calling a pro, here are a few simple tests that can sometimes fix the problem and avoid unnecessary service charges. This guide covers easy steps to try first, so you can get heat back fast or know when it’s time to call for help.
Safety First: Before You Touch Anything
A simple inspection of your furnace can identify the issue, but safety needs to be your number one priority. Gas- or electric-powered furnaces each have their own inherent dangers. A little preparation before touching anything goes a long way to protect you and your home.
Turn Off Furnace Power
Turn off furnace power. Locate the switch on the unit or turn off the correct breaker in your panel. Listen for a clicking noise or check for any indicator lights to confirm that it is off.
To add an additional layer of safety, implement a lockout or tagout so that no one can accidentally switch it back on. Note the date you switch it off. This will help you document what you’ve done in case you have to call on someone else for assistance down the road.
Gather Your Basic Tools
Gather the basic tools before you get started. An inexpensive screwdriver, flashlight, and a multimeter will suffice for most inspections. Wear gloves and goggles to protect yourself first, especially if you will have to look inside the unit.
If you’re going to scrub the filter or clean the flame sensor, have a soft bristle brush and a vacuum located nearby. Place all your tools into a shoebox or project box so you can keep better track of what you have and avoid losing tools.
Know Your Furnace Type (Gas/Electric)
Gas and electric furnaces have different components and issues. Your user manual has specific information on what to look for and what the dangers are with your particular model.
If you have a gas furnace, make sure you know where the shut off valve is located in case you smell gas. Electric units require more caution with wiring. Never attempt to operate the equipment with the door or front panel removed or unsecured.
Quick Wins: Simple Checks to Try
When symptoms and signals occur, like a furnace not turning on, a quick checklist will help you diagnose the issue quickly. These simple checks require minimal expertise or equipment. They can save time and reduce caregiver stress before reaching out for assistance.
By checking each item off the list, you’re eliminating possible problems and determining when it’s time to look elsewhere.
Is Your Thermostat Talking?
Go to the thermostat first. Ensure that it is plugged in, and that it’s on “heat.” Often, someone accidentally knocks the setting or the batteries are dead and the furnace doesn’t turn on.
The display should come on and provide easy-to-read numerical values. Set the temperature a few degrees above the current room temperature and then listen for your furnace to click on. If they don’t, examine the wires connected to the back of the thermostat.
Check for any loose or frayed wires, which can cut off the signal. If you are able to, try to carefully push them back into position. This simple step fixes many start-up problems right away because the thermostat is what instructs the furnace to perform in the first place.
Check the Furnace Switch
Next, locate the furnace switch, which is usually found by the unit, either on a wall or ceiling. It should resemble a regular light switch. Check to ensure it’s in fact “on.
Occasionally, a cleaning person bumps the switch off. If the switch appears old or is sticky, flip it to off, then back on to reset. A simple reset might bring it back online if it tripped.
Look at Your Circuit Breaker
Visit your breaker box. Check for breakers clearly marked “furnace” or “HVAC.” If any of them are out of alignment or in the neutral position, toggle them to “off,” then back to “on.
It’s true that a tripped breaker or blown fuse can kill power. If it does trip again, make a record of this and go get assistance. Log what you notice to report back to your tech.
Furnace Dead? Your DIY Fix-It List
When your furnace is dead, you’ll know it—there’s nothing like an emergency repair with cold weather fast approaching or a cold week already in the books. Here’s a quick troubleshooting guide to get you started with some simple checks and fixes to try before calling in a pro.
Manuals can be found online, and these steps don’t require advanced tools, only a little patience and attention. Keeping a record of what you’ve already tested goes a long way in reducing unnecessary confusion should you need to make the call.
Read on for a rundown of the most DIY-able furnace fixes. They’re listed from most simple to more detailed, and they usually work for the average American homeowner—from a basement in Los Angeles to an attic in the Northeast.
1. Inspect the Thermostat Settings (Again!)
Thermostats are still the most common culprits for furnace malfunction. It’s amazing how easy it can be to forget a wrong setting or a previous schedule still being followed.
Make sure the thermostat is in “heat” mode and that the desired temp is higher than the current room temperature. Sometimes, programmable thermostats revert to outdated schedules or are knocked off schedule after a power outage.
Try toggling the temperature up and down a few degrees and watch for a click or response from the furnace. If it still does not respond, inspect the batteries if your thermostat is battery-powered.
We know a dead battery can kill the signal, but they fair worse entirely. Checking these items out first can save you time and prevent an unwanted service call.
2. Replace or Clean Your Air Filter
A clogged air filter can restrict airflow, causing the furnace to shut off as a safety feature. To see if your filter is clogged, remove the filter—usually located where the return duct connects with the furnace.
If you’re unsure, hold it up to a bright light. If you can’t read the newspaper through it, it’s time to replace them. Disposable filters should be disposed of and replaced, and reusable filters should be washed according to the manufacturer’s guidelines.
Don’t wait for someone to remind you—if it’s been a few months or you notice dirt and dust accumulating, just do it already. Replacing or cleaning the air filter is an inexpensive fix that can improve airflow, and it frequently brings a furnace back to life.
Changing your air filter regularly—every 1-3 months depending on usage and dirt levels in your area—can avoid a large majority of common furnace problems.
3. Check the Furnace Power Switch (It’s Easy to Miss!)
Furnaces typically have a power switch that looks like a light switch. You can typically locate it on or near the unit, or at the top of a basement stairwell.
It’s easy for this switch to get flipped off by mistake when you’re moving boxes or vacuuming. Verify that it’s in the “on” position. Check for any damage or wear—such as a switch that seems loose or won’t stay toggled on.
The furnace switch shouldn’t be inaccessible due to boxes or chairs. To prevent any future annoyance, make sure that you label it so no one confuses it with other switches nearby!
If your furnace is still dead, look in the home’s breaker panel. Overloads or nearby electrical work could have tripped the furnace’s breaker or blown a fuse.
4. Reset Your Furnace Unit
Many modern furnaces come equipped with a reset button, typically located on your furnace’s main control panel. Clicking the button per your manufacturer’s instruction booklet may reset basic faults and reboot the entire unit.
After you reset, give it some time and listen for the fan or burners to start up. Note down the time and what you hear when it happens—these notes will help a technician if you ever need one.
If your furnace needs resetting often, that could indicate an underlying electrical or component problem that should be addressed. Make sure you turn the power off first before removing any access panels.
Most furnace make models include safety switches to automatically deactivate the unit when a door is removed!
5. Examine the Pilot Light (Gas Furnaces)
Only gas furnaces have a pilot light, and it should burn with a consistent blue flame. If gas is available, set the gas control to “pilot.” Allow five to ten minutes for gas to clear, then relight per the instructions on the label.
If you see a weak or yellow flame, it’s time to clean up. You’ll want to use a soft cloth and careful pressure to avoid damaging the flame sensor or pilot assembly!
In addition, check the thermocouple, the small metal rod that extends into the pilot flame. If so, it’s either loose or dirty, meaning the pilot won’t stay lit.
By performing these checks, you ensure that your furnace is operating safely and consistently. Be sure to allow the space to vent any gas before attempting to relight to avoid fires or other dangers.
6. Look for Blocked Vents or Registers
Blocked vents or registers can cut off airflow. This will cause the furnace to appear as if it is dead when in fact the furnace is doing its job.
Visit each room in your house and make sure that furniture, rugs, or moving boxes aren’t obstructing heat supply and return vents. Check that all vents or registers are open and unblocked.
Dusting them off can do wonders, as buildup can dramatically decrease efficiency. Just a little vacuuming with each season change stops troubles before they start.
In homes with animals or high foot traffic, such as through a mudroom, vents can frequently become blocked.
7. Check the Condensate Drain Line
High-efficiency furnaces produce condensation that needs to drain away, usually through a small plastic or rubber tube. If this line becomes clogged, a safety switch should prevent the furnace from operating.
Locate the drain line near the base of your furnace and inspect for water buildup or musty odors. Remove any obvious obstructions and make sure the line slopes downward to drain correctly.
If water is pooling under or around the unit, mop it up and watch for signs of leaks. Routine inspections and maintenance help your system run smoothly and reduce the likelihood of unexpected breakdowns.
Decode Your Furnace’s Language
Your furnace may give you warning signs well in advance of a total breakdown. By learning to read these signs, you’ll be able to notice minor issues before they grow into major repairs. Intelligent troubleshooting inevitably begins with the essential. Most modern furnaces will communicate their malfunction through blinking lights or error codes. Weird sounds might be your best bet when it comes to diagnosing what’s broken.
Understanding Blinking Lights
The majority of contemporary furnaces have a series of blinking lights to indicate the status of your furnace. Your furnace’s owner’s manual should include a decoder for these light codes. Typically, an unblinking green indicator light indicates that the system is operating normally. Conversely, quick blinking could mean a safety switch is open or has failed.
Write down the exact pattern—such as three quick blinks, pause, then two slow blinks. This comes in handy if you have to speak about your problem to a professional. Knowing what different patterns mean will save you time in troubleshooting the problem. It could be that you need to tighten a loose access panel or replace a clogged filter.
A good, quick way to see if your filter is clogged is to hold it up to a bright light.
What Error Codes Mean
Furnaces give error codes to lead you directly to the issue at hand. These may be displayed on a small digital screen, or as a pattern of blinking lights. Always check the manual for what the code means. Some errors just need a power reset, others mean you should call for help.
Write down any repeating codes, as this aids if/when a technician makes a house call. If you have a portable generator, note that absence of a ground-neutral bond causes startup failures. On top of that, a dirty power supply can be a culprit as well.
Listening for Unusual Noises
Step 3 – Listening for Unusual Noises With the inducer fan, a very quiet humming noise or soft whoosh is expected. If you’re hearing banging, screeching or rattling, that is usually a sign that something’s wrong. In other cases, a loose access panel or a stuck combustion blower fan could be the culprit.
If you notice unusual sounds, try to get them on your cellphone. This provides an easier entry point for a technician to troubleshoot. Make sure that the wires to the thermostat are fastened properly, as loose wires can occasionally lead to unusual noises or difficulties when starting up.
Keep Your Furnace Happy Long-Term
A properly maintained furnace does more than just keep your home warm. Proper maintenance will help keep your unit safe, operating efficiently, and extending its lifespan. In Los Angeles, where winters can be mild but cold nights suddenly arrive, a dependable furnace is essential. Creating good habits today will result in less money, time, and stress spent tomorrow.
Why Regular Maintenance Matters
Regular inspections and maintenance prevent most major issues from occurring. Replace your furnace filters 1-3 times a month (or every 90 days if you’re pet-free). This simple act prevents dust and debris from entering your home!
When filters are clean, there’s less strain on your heating system, improved airflow, and lower energy bills. Clean the flame sensor every 6 months! When you do the maintenance at least once a year, you’ll help your furnace light and function properly.
Safety should be your highest priority—always verify that the furnace door and front panel, which have shutoff switches, don’t interrupt the system. A little time for these maintenance steps will ensure safe and efficient operation of your home furnace long-term. It reduces the chances of fires or gas leaks occurring.
Schedule your annual maintenance in the spring or summer months for quicker, less expensive service.
Simple DIY Upkeep Tips
A simple checklist is all it takes! Change your filters, dust off the vents, remove clutter from around your furnace and check the thermostat wires for frays.
Go digital! Set reminders on your phone to change filters and check in-season each spring and fall. Involve everyone! Share maintenance tasks with the whole family to help keep them engaged and your furnace on people’s minds.
These simple tasks run interference on calamity, ensuring you stay cozy when it counts.
Schedule Annual Professional Tune-Ups
Just like any other machine, your furnace needs regular maintenance. Schedule Annual Professional Tune-Ups to ensure everything is operating properly.
Mention any strange noises or behaviors you observed. They’ll catch leaks, test safety switches and ensure everything is operating properly. Maintain a file of all service dates and repairs for easy access.
Know When to Call the Pros
Understanding when to leave it to the pros can help you avoid wasting time, money, and aggravation. Though most furnace breakdowns are easily solvable, others require professional intervention. Safety is paramount, particularly with issues that involve gas, electric, or intricate mechanical issues.
Persistent Problems After Troubleshooting
You’ve already gone through all the easy troubleshooting steps – replace the air filter, check the thermostat, reset the breaker. If the furnace refuses to start, it’s time to call the pros. Going through the same troubleshooting steps is not going to solve a bigger problem and in some cases could make things worse.
Keep a simple record of things you’ve done and changes you observed. All of this information will assist the technician in diagnosing the issue sooner. Don’t remove or mess with panels or wiring unless you’re a trained professional—it can result in far worse problems or serious harm.
Strong Gas Smells or Loud Noises
A strong gas smell or loud banging noises from the furnace should be alarming signals. For gas, evacuate the area immediately and call your gas provider or 911. Avoid turning on any lights or electronics near a suspected leak. Protecting the safety of everyone in the home should be our first concern.
Allow professionals to determine the site is safe before you attempt to inspect the furnace once more.
Electrical Issues Beyond Breakers
If you’re noticing blown fuses, burnt wires, or lights flickering on and off, it’s time to call an HVAC technician. Do-it-yourself home repairs to electrical issues are dangerous and can void warranty coverage. Document everything you observe, but don’t attempt do-it-yourself repairs without professional training.
Chronic electrical issues require a pro’s corrective touch to avoid dangers.
When You’re Just Not Comfortable
When you’re just not comfortable, it’s just not worth it to try a dangerous project and potentially cause serious damage, or worse, injury. Have the contact information for local HVAC professionals you trust readily available. They are able to take on more difficult or emergency repairs and provide warranty coverage.
Conclusion
We understand, figuring out why your furnace suddenly stopped working can be annoying. In reality, most repairs are just a few minutes away! Start with the fundamentals, pay attention to unusual noises, examine the thermostat. Sometimes all it takes is clean filters or a reset flipped breaker to get your heat back quickly. Because Los Angeles residences experience large extremes in temperature, a properly functioning furnace is an important feature in maintaining healthful levels of comfort. If it starts looking strange or you detect a gas smell, contact a professional immediately. There’s no shame in calling someone else to help. Save yourself some money and time, and try these steps first, though. You’d be surprised how often this saves you both money and aggravation. Looking for more useful tips, or need to tell us about your weird furnace? We’d love to hear from you, so get in touch. Whatever the case may be, we hope that you stay warm—and safe—out there.
Frequently Asked Questions
Why won’t my furnace turn on even though the thermostat is set?
Make sure your thermostat is powered on and that it’s in “heat” mode. Dead batteries or wrong programming can prevent your furnace from turning on.
Is it safe to troubleshoot my furnace myself?
Is it safe to troubleshoot my furnace myself? Don’t open panels or mess with gas/electrical connections unless you know what you’re doing.
What should I check before calling a furnace repair professional?
Make sure your thermostat is functioning properly. Check that your furnace switch is in the ‘on’ position, your breaker hasn’t tripped and your filter is clean! Again, these checks are simple and completely safe.
How often should I replace my furnace filter in Los Angeles?
Replace or clean your filter monthly, more often during high use months. Change it every 1–3 months to keep your furnace running its best and to prevent local dust and wildfire ash from clogging your filter.
What do flashing lights or error codes on my furnace mean?
They are warnings sent by your furnace. Consult your furnace manual for code interpretations. If the code is not obvious, contact a professional for assistance.
Why is regular furnace maintenance important in Southern California?
If you live in a warmer climate, dust and debris can still get caught in your furnace. Preventative maintenance improves efficiency, safety and can help your system last longer.
When should I call a professional for furnace problems?
Call if your furnace still won’t turn on after basic checks, you smell gas, or you see unfamiliar error codes. Safety first—don’t take chances on repairs you’re unqualified to make.