Whether it’s a leaky furnace or if you flip the switch to start your heating system when it gets chilly and it won’t start, common furnace problems can strike your home at any moment.

Regardless of the issue, knowing how your heating system works and a little bit about some frequent furnace problems is crucial in deciding whether you can troubleshoot on your own or if you need professional services. By observing the furnace's behavior, listening for peculiar noises and checking for signs of damage or blockage, you can narrow down the possible causes.

If you're not sure about the problem or lack the necessary skills and tools, it's best to call a reputable HVAC company like Connolly Electric & Mechanical. We can accurately pinpoint the issue and complete the required repairs or maintenance, so we can get your furnace working again ASAP.

Here's more about what causes a furnace to leak water and eight other common heating issues:

1. My Furnace Is Leaking Water

A furnace can leak water for several reasons. One possibility is a condensate leak, where the water produced during the combustion process is not completely draining away. This may be due to a blocked condensate drain line or a failing condensate pump. Another potential cause of water leakage from a furnace is a cracked heat exchanger, which can be responsible for water—as well as dangerous gases—coming out of the furnace.

It is imperative to address water leaks immediately to prevent additional damage to your furnace. Contacting a professional HVAC technician like the crew at Connolly Electric & Mechanical is recommended to diagnose and resolve the issue successfully.

2. My Furnace Makes Cold Air/Lack of Heat

Some possible causes for a furnace blowing cold air or not blowing hot air could be a malfunctioning thermostat, a problem with the pilot light or ignition system, a clogged air filter, or a malfunctioning heating element. It also may be your furnace is overheating and shutting off as a safety precaution.

If your furnace will not blow hot air, it's better to contact a trained HVAC tech to diagnose and fix the problem. They can provide an accurate assessment and suggest the correct solution.

3. My Furnace Can't Keep Up

A widespread reason your furnace isn’t keeping up on a cold day is that your home doesn’t have enough insulation, which can cause heat loss and decreased efficiency. Another reason your furnace is struggling is because it’s not powerful enough for your home, so it can’t generate enough heat to adequately warm the space. A malfunctioning thermostat or ductwork problems can also cause uneven heating.

To address this, first look at your home’s insulation level and make sure it’s enough to insulate your home. Also, look at the thermostat to see if it’s set right and the batteries aren’t dead.

If the problem continues, consider contacting an experienced HVAC company, such as Connolly Electric & Mechanical, who can assess your system, determine the root cause and provide solutions such as furnace replacement, repairing ductwork or changing your thermostat settings.

4. My Furnace Isn't Running at All

If your furnace is not working, there are a few steps you can take to troubleshoot before phoning a professional. Check if the thermostat is set properly and the batteries are good. If the furnace still doesn't power on, check the circuit breaker or fuse box to make sure power is reaching the unit.

If there is power but your furnace won't blow hot air, the problem may be with the ignition system or gas supply. In that case, it's better to consult a seasoned HVAC technician for diagnosis and repair.

5. My Furnace Is Short Cycling

If your furnace is short cycling, it means it is turning on and off often at short intervals instead of running in regular cycles like it is designed to do. This can result in inefficiency, more energy use and potential damage to your heating system.

If you think your furnace is short cycling, the first step is to pull out your unit’s air filter. Filters should be exchanged regularly to ensure air flow, so if your furnace air filter is clogged with debris you should exchange it for a clean one—and make sure it is pointing in the right direction. If that doesn’t do the trick, go to your thermostat and make sure  it’s set right and the batteries are good.

If those two things don’t work, it’s a good idea to call experts like the staff at Connolly Electric & Mechanical. Quick professional attention will help restore the proper functioning of your furnace and prevent additional complications and high energy bills.

6. My Furnace Won't Stop Humming

When your furnace is making a humming noise, it often is a sign of a malfunction with the electrical hardware or the blower motor. Therefore, if you notice your furnace making a humming noise, it is critical to take action.

If the noise doesn't go away, it is better that you  get in touch with a professional HVAC technician.

7. My Furnace Makes Loud Noises

If your furnace is making a persistent loud noise, it's important to address the issue quickly to prevent further damage or potential safety hazards.  One common reason is a broken blower motor or fan, which can create a grinding or screeching sound. Another possible cause is a loose or worn-out belt that may emit a squealing or rattling noise.

Because of the complexity of furnace systems and potential risks involved, it's best to consult with a heating and cooling specialist.

8. My Furnace Is Not Turning On

If your furnace refuses to turn on, make sure the thermostat is set to the desired temperature, is in heating mode and the batteries are working. Then, see if the circuit breaker or fuse that controls the furnace is sending power to the unit. If these basic checks don't resolve the problem, you can examine the furnace's power switch or emergency shutoff switch to ensure they're in the "on" position and weren’t accidentally turned off.

If those steps don’t do the job, contact a heating specialist for furnace repair.

9. My Furnace Won't Ignite

Much like a furnace that won't turn on at all, a furnace that isn’t igniting can be the result of a clogged air filter or a tripped circuit breaker. So, checking out the air filter and assessing your circuit breakers are a good place to start.

Other common causes of a furnace not igniting could be a faulty igniter or faulty flame sensor. Indications of these include the furnace repeatedly trying to ignite without success, a lack of heat production or the furnace is making a burning or gas smell. Both of these issues can be simply addressed by HVAC professionals like the team at Connolly Electric & Mechanical.