TOP 10 FURNACE PROBLEMS: YOUR TROUBLESHOOTING GUIDE
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Has this ever happened to you? The weather takes a chilly turn, so you go over to your furnace for the first time in months and turn it on. You expect to feel warm air wafting through your home, but you get cold air or strange noises instead.
Furnace problems can occur at any time and for a variety of reasons. Fortunately, there are often easy solutions. Sometimes a cleaning session or a few tweaks to your system can resolve the issue and provide you with the heat you need.
Blue Dot Services is a Maryland-based heating, cooling, and plumbing business with over 40 years of experience helping homeowners fix their heating problems. We offer everything from heating installation to heating repair to keep you warm in Maryland’s frigid, windy winters.
Our furnace troubleshooting guide will look at the most common furnace problems, their likely causes, and simple steps you can try.
Need a faster solution? Call our team today to schedule a quick furnace inspection.
TOP 10 FURNACE PROBLEMS: A TROUBLESHOOTING GUIDE
Figuring out your furnace issues generally requires the process of elimination. If one of these solutions doesn’t work, try another to narrow down what could be causing the problem.
1. PROBLEM: MY OIL OR GAS FURNACE ISN’T WORKING
Got a no-heat problem? If your furnace is not turning on, or if it does turn on but doesn’t produce heat, be sure to check the following to see if they could be causing your furnace issue:
Thermostat Settings Too Low: Your thermostat settings could be too low and, as a result, more heat isn’t being “requested” from the furnace. Double-check that your thermostat is in heat mode and is set at the appropriate temperature.
Thermostat Working Fine: If your thermostat is working just fine, fiddle with the temperature setting by moving it higher or lower. Sometimes older furnaces need a bigger temperature swing before they start responding. If this still doesn’t fix the issue, you may need to have your thermostat replaced.
A smart thermostat can provide you with more accurate readings and even helpful features like pre-programmed schedules for when you’re out of the house.
Tripped Circuit Breaker: Is your circuit breaker or fuse tripped or blown? Look at your fuse box to see if it’s tripped. If so, reset your circuit breaker. If you have a blown fuse, replace the fuse with professional help.
Pilot Light Out: Is your pilot light out? If so, turn the furnace off and wait at least five minutes before attempting to relight it. This typically involves locating the gas control knob, switching it to the pilot setting, and holding down the reset button according to the manufacturer’s instructions. Once the pilot light is back to normal, return the gas valve to its usual setting, then you can use your furnace again.
Don’t feel comfortable relighting the pilot light or checking the circuit breaker? Schedule service online with Blue Dot, and we’ll be happy to take care of the issue for you.
2. PROBLEM: NO HEAT FROM FURNACE (OR FURNACE TURNS ON, BUT STILL NO HEAT)
If your furnace isn’t starting, or if it turns on without emitting heat, be sure to check the following causes. There are a few possible reasons that could explain why your furnace is running, but no heat is being produced.
Wrong Thermostat Setting: Similar to the first section, your thermostat setting might be too low, so your furnace isn’t getting the signal it needs for more heat. Switch your thermostat to heat mode or increase the temperature setting.
Thermostat Isn’t Sensitive Enough: Move the temperature up or down a few degrees to see if your furnace turns on. If not, you may need a new thermostat.
Tripped Circuit Breaker or Blown Fuse: Look at your fuse box to see if it’s tripped. If so, reset your circuit breaker. If it’s blown, replace the fuse.
Pilot Light Out: Is your pilot light out? If so, relight the pilot light.
3. PROBLEM: LOW, WEAK HEAT
Sometimes your furnace will turn on and produce heat, but it’s weak and barely seems to warm your home at all. These heater problems can be frustrating since you’re close, yet still so far from what you need. Let’s take a look at what could be causing it and whether you should get professional help.
Old Age: Is your furnace over 10 years old? Very old models usually operate on worn-out parts and have outdated energy efficiency ratings that can’t meet your needs. You’ll have to reach out to a professional to get a new furnace installed.
Poor Airflow: Your furnace may not be the problem. A home with clogged ductwork or poor airflow can fail to warm up. You may also have a lot of cracks in your windows or the foundation that are spilling out heat. Inspecting your ductwork, doors, and windows for flaws and patching them up will fix this problem easily.
Improper Sizing: Your furnace may be producing weak heat because it’s too small for the space it’s in. You may need to look into a new furnace installation or try a secondary heating source.
4. PROBLEM: PILOT LIGHT IS AN ODD COLOR
Your pilot light should be tall and bright blue when your furnace is on. This color comes from a flame that’s receiving the right amount of oxygen, so any other color is cause for concern.
Yellow Flame: A yellow pilot light means your furnace is not receiving enough oxygen. The intake valve is likely clogged with dirt or dust, so you’ll need professional help to clean it out.
Orange Flame: This color may indicate the furnace is producing some carbon monoxide. Carbon monoxide has no odor or taste but is extremely hazardous and needs to be taken seriously. Reach out to a heating and cooling service to have a professional inspect your unit for old age or damage.
Weak Light: If the light is the right color, but small and weak, you may have a gas pressure problem or a dirty thermocouple that needs cleaning.
It’s important to note that yellow and orange can look quite similar at a glance. Even a yellow flame could mean the beginnings of a carbon monoxide leak. It’s better to be safe than sorry, so call for professional help. Contact Blue Dot to get an inspection and fix the issue safely.
5. PROBLEM: NOISY FURNACE (AND YOU’RE NOT SURE WHY)
A furnace is normally pretty quiet, so unexplained noises usually indicate a problem. Furnace troubleshooting should involve listening to your unit closely while it’s on to figure out which strange noise you’re dealing with.
Squealing Noises: A squealing noise could be caused by a loose blower belt. Check the belt to see if it depresses about one inch at the center of its span.
If not, it should be tightened. If it’s frayed, replace it. The squealing may also be caused by motor or shaft bearing parts that need oil. They are usually located at the end of each shaft. Simply oil them with a light oil and cloth.
Rumbling Noises: A rumbling noise may stem from dirty gas burners or a poorly adjusted pilot light. In either case, you should call a professional service technician to fix the problem.
Dirty Filters: Your furnace may simply be noisy because the filter needs to be replaced. Find the filter in the unit and either replace or clean it.
6. PROBLEM: BLOWER MOTOR CONSTANTLY RUNNING
Is the blower constantly running? A few common gas furnace troubleshooting items to check are below.
Dirty Filters: Do you have a dirty air filter in your furnace? This could cause your furnace not to achieve the temperature setting you have your thermostat set to, and to constantly run. Simply replace your filter to fix the issue. Filters should be replaced every two to three months.
Dirty Gas Burner: Are your gas burners dirty and in need of adjustment? While you could clean the gas burners yourself, it is best to leave this to the experts. You could greatly damage your furnace if this procedure is not done correctly.
Lack of Oil: When’s the last time you oiled your blower motor? If your gas furnace comes on or off too frequently, it may be because the parts in your blower motor need a little oiling. These parts are usually at each end of the shaft. Simply oil them using a light oil and a soft cloth.
Loose Furnace Belt: Is your furnace belt properly tightened? If the belt in your gas furnace is too loose, your furnace will not run properly. The belt should depress about one inch at the center of the belt span. If it’s too loose, simply tighten it. If it’s frayed, it will need replacement.
Wrong Thermostat Setting: Is your thermostat set to “fan continuous”, or is it faulty? If the fan is set to continuous, simply change the fan setting to “auto” on the thermostat.
7. PROBLEM: THERMOSTAT NOT WORKING (AND OTHER THERMOSTAT ISSUES)
The thermostat is the control device that determines when your furnace should turn on and off. It’ll also help you adjust settings to get the right amount of heat when you need it. If your furnace isn’t turning on or producing heat, it may be because you have a broken thermostat.
Do some furnace troubleshooting with these common contributors to faulty thermostats.
Wrong Mode: Is your thermostat in heat mode or not set at your preferred temperature setting? Move the temperature up or down a few degrees to see if your furnace turns on.
Old Batteries: Do the batteries on your thermostat need to be replaced? Swap them out and see if that fixes the issue.
Wrong Thermostat Location: Is your thermostat in a drafty hallway or by an outside heat source that could be affecting its performance? If so, consider moving the thermostat to a spot that is not affected by outdoor areas or temperatures.
Do you need extra insulation to fix your digital thermostat problems? To find out, try turning off the power to both the thermostat and heating system. Remove the thermostat cover and see if any cool or warm air comes through. If so, remove the entire unit and caulk or add extra insulation around the opening.
Make sure your thermostat is clean of dust and dirt. Using a small toothbrush or paintbrush, clean the small metal plates (the contacts) within the unit. Do not touch these contacts, or any other interior parts, with your fingers.
Check wires in the thermostat for corrosion. If you find any, remove the wires and clean them using a wire stripper.
8. PROBLEM: FURNACE SUDDENLY TURNS OFF
A furnace should only turn on and off when you tell it to. If it suddenly shuts off, that almost always points to a problem you need to take a look at immediately. The issue may be something minor you can fix on your own, but it might also need a professional eye.
Clogged Filter: Sometimes a furnace turns off because the filter is too dirty and it can’t achieve proper airflow. The shut-off feature is a safety measure to avoid overheating, so you can easily fix this issue by swapping in a clean filter. We recommend changing your furnace filter every three months.
Dirty Flame Sensor: One of the most common furnace problems is a dirty flame sensor. If the furnace can’t detect a correctly functioning flame, it’ll shut off to reduce the risk of an accident. Reach out to a professional to have them open up your furnace and clean the flame sensor.
Broken Thermostat: Sometimes your thermostat is damaged and tells the furnace the right temperature has been achieved, even if your home is stone cold. Getting a professional to swap out an old thermostat for a new model should clear up the issue.
Damaged Heat Exchanger: Heat exchangers are crucial to make sure the furnace can produce hot air and circulate it into your home. If your heat exchanger is damaged, its built-in safety features will turn the system off to avoid a safety hazard. You always need a professional to inspect the heat exchanger to reduce the risk of a carbon monoxide leak, a fire, or melted parts.
9. PROBLEM: FURNACE CYCLES FREQUENTLY
Furnace problems are always trying to tell you something. A furnace that keeps turning on and off is a sign of the unit trying and failing to resolve a deeper problem.
Dirty Filters Causing Overheating: A furnace on the brink of overheating will turn off until the system cools down. If it keeps overheating and starts cycling on and off, you should inspect the filters to see if they’re dirty or clogged. If they are, swap them with clean filters to help the system cool itself down.
Improper Size: Your furnace might be too large or small for the space it’s in. A furnace that’s too small may constantly cycle on and off in an attempt to reach a higher temperature it’s not capable of, running continuously and eventually overheating. One that’s too large may turn off too quickly since it can heat much faster.
Clogged Exhaust Vent: A furnace with a clogged exhaust vent can cause cycling or a full-system shutdown. Debris like snow, leaves, or rodents can all get into this vent, so you’ll need to check it manually and see if you can dig out anything that might be lodged inside.
Malfunctioning Thermostat: Your thermostat may be faulty or old, sending out inaccurate readings that turn your furnace on and off. It may also just need a little calibration. Fiddle with the settings to see if it responds properly to more dramatic temperature changes. If nothing changes, reach out to a professional.
10. PROBLEM: FURNACE EMITS STRANGE ODORS
Your furnace may occasionally smell a little dusty if you haven’t used it in a while. However, the odor should never be foul or intense. These furnace problems almost always require a professional eye, so let’s take a look.
Musty, Old Odors: This scent can mean a very dirty or moldy filter. If you haven’t changed your filters in a while, insert clean ones and see if that improves the smell.
Rotten Eggs or Sulfur: This odor is extremely serious and needs a professional on the case immediately. You likely have a gas leak that needs to be tended to, so turn your furnace off and keep it off until you get help.
Metallic or Burning Smell: This odor usually points to an electrical failure or melting inner parts. You’ll need a professional to inspect your unit before the furnace gets even worse.
BLUE DOT CAN HELP YOU FIX YOUR FURNACE PROBLEMS
Furnace troubleshooting can be stressful, especially if you’re completely new to the process and don’t want to accidentally make the issue worse. Blue Dot provides fast access to experienced technicians who can safely inspect your system and find the fix you need.
Not only can we help fix your furnace, we also provide HVAC installation if you need new heating and cooling options.
All our customers get access to our discounts and Pro Service Plans to help them budget for essential furnace repairs, maintenance, or new installations.
Can’t fix your furnace problems? Give us a call or schedule your appointment online so an experienced furnace technician can get to the bottom of the issue.