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

Regardless of the cause, understanding how your heating system works and a little bit about some typical furnace problems is crucial in deciding whether you can troubleshoot on your own or if you need professional assistance. By monitoring the furnace's behavior, listening for strange 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 an experienced HVAC company like Connolly Electric & Mechanical. We can accurately pinpoint the issue and execute the required repairs or maintenance, so we can get your furnace up and running ASAP.

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

1. My Furnace Is Leaking Water

A furnace can leak water for many reasons. One possibility is a condensate leak, where the water released during the combustion process is not completely draining away. This might be due to a blocked condensate drain line or a broken condensate pump. Another likely cause of water leakage from a furnace is a cracked heat exchanger, which can be responsible for water—as well as dangerous gases—escaping from the furnace.

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

2. My Furnace Is Blowing Cold Air/Not Blowing Hot Air

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

If your furnace will not blow hot air, it's a good idea to contact a trained HVAC technician to diagnose and fix the problem. They can provide an accurate assessment and advise you on the proper solution.

3. My Furnace Is Not Keeping Up

A frequent reason your furnace isn’t keeping up on a cold day is that your home is lacking insulation, which can cause heat loss and reduced efficiency. Another reason your furnace is having difficulties is because it’s too small for your home, so it can’t generate enough heat to effectively warm the space. A broken thermostat or ductwork problems can also result in insufficient heating.

To correct this, first assess your home’s insulation level and make sure it’s enough to keep warm air in and cold air out of your home. Also, look at the thermostat to make sure it’s set right and the batteries still function.

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

4. My Furnace Is Not Working

If your furnace is not working, there are a few steps you can take to troubleshoot before contacting a pro. Ensure the thermostat is set correctly and the batteries are not dead. If the furnace still doesn't start, check the circuit breaker or fuse box to make sure power is reaching the furnace.

If there is power but your furnace won't blow hot air, the problem may rest with the ignition system or gas supply. In that case, it's a good idea to contact an experienced HVAC technician for diagnosis and repair.

5. My Furnace Is Short Cycling

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

If you suspect your furnace is short cycling, the first step is to look at your unit’s air filter. Filters should be changed regularly to ensure air flow, so if your furnace air filter is plugged with dirt you should exchange it for a clean one—and make sure it is pointing in the right direction. Next, look at your thermostat and look to see if  it’s set right and the batteries are good.

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

6. My Furnace Is Making a Humming Noise

If your furnace is making a humming noise, it often is an indication of an issue with the electrical hardware or the blower motor. Therefore, if you notice your furnace making a humming noise, it is crucial to take action.

If the noise continues, it is best to  contact a professional HVAC technician.

7. My Furnace Is Making a Loud Noise

If your furnace is producing a constant loud noise, it's important to address the issue quickly to prevent further damage or potential safety concerns.  One common reason is a broken blower motor or fan, which can make a grinding or screeching sound. Another common 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 safer 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 take care of the problem, you can inspect 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 get the job done, call a heating specialist for furnace repair.

9. My Furnace Is Not Igniting

Similar to a furnace not turning on at all, a furnace that isn’t igniting can be caused by a plugged air filter or a tripped circuit breaker. So, checking out the air filter and taking a peek at your circuit breakers are a good place to start.

Other common causes of a furnace not igniting are a faulty igniter or faulty flame sensor. Indications of these include the furnace continually attempting 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 fixed by HVAC professionals like the team at Connolly Electric & Mechanical.