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

Regardless of the problem, understanding how your heating system works and a little bit about some common furnace problems is vital in deciding whether you can troubleshoot on your own or if you need professional support. By watching the furnace's behavior, listening for unusual 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 AZ Air Conditioning and Heating. We can accurately diagnose 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 prevalent 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 created during the combustion process is not completely draining away. This could be due to a blocked condensate drain line or a malfunctioning condensate pump. Another likely cause of water leakage from a furnace is a cracked heat exchanger, which can result in water—as well as dangerous gases—leaking out of the furnace.

It is necessary to manage water leaks quickly to prevent further damage to your furnace. Consulting with a professional HVAC technician like the crew at AZ Air Conditioning and Heating is recommended to diagnose and resolve the issue effectively.

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

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

If your furnace does not blow hot air, it's best to contact a professional HVAC technician to diagnose and fix the problem. They can give an accurate assessment and recommend the proper solution.

3. My Furnace Is Not Keeping Up

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

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

If the problem continues, consider contacting an experienced HVAC company, such as AZ Air Conditioning and Heating, who can inspect your system, determine the root cause and provide solutions such as furnace replacement, repairing ductwork or modifying your thermostat settings.

4. My Furnace Is Not Working

If your furnace is not working, there are a couple of steps you can take to troubleshoot before phoning a heating specialist. Make sure the thermostat is set right and the batteries are not dead. If the furnace still doesn't start, check the circuit breaker or fuse box to verify power is reaching the furnace.

If there is power but your furnace won't ignite, the problem may rest with the ignition system or gas supply. In that case, it's best 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 multiple times at short intervals rather than running in regular cycles like it should. This can result in inefficiency, higher energy bills and potential damage to your unit.

If you suspect your furnace is short cycling, the first step is to pull out your unit’s air filter. Filters should be changed when they are dirty 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. Next, 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 best to call experts like the team at AZ Air Conditioning and Heating. Prompt professional attention will help restore the proper functioning of your furnace and avoid more complications and high energy bills.

6. My Furnace Is Making a Humming Noise

Whenever your furnace is making a humming noise, it often is a sign of a malfunction with the electrical parts or the blower motor. Because of this, if you hear your furnace making a humming noise, it is crucial to take action.

If the noise continues, it is better that you  employ a professional HVAC technician.

7. My Furnace Is Making a Loud Noise

If your furnace is emitting a persistent loud noise, it's important to deal with the issue quickly to prevent further damage or potential safety risks.  One common reason is a malfunctioning blower motor or fan, which can make a grinding or screeching sound. Another potential cause is a loose or worn-out belt that may produce a squealing or rattling noise.

Because of the complexity of furnace systems and potential risks involved, it's safer to get a hold of a heating and cooling specialist.

8. My Furnace Is Not Turning On

If your furnace won't turn on, make sure the thermostat is set to the preferred temperature, is in heating mode and the batteries are functioning. Then, check if the circuit breaker or fuse that goes to the furnace is working right. If these basic checks don't fix the problem, you can inspect the furnace's power switch or emergency shutoff switch to verify they're in the "on" position and weren’t accidentally turned off.

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

9. My Furnace Is Not Igniting

Like a a furnace that will not on at all, a furnace that isn’t igniting can be caused by a dirty air filter or a tripped circuit breaker. So, inspecting the air filter and assessing your circuit breakers are a good place to start.

Other potential causes of a furnace not igniting could be a faulty igniter or malfunctioning flame sensor. Symptoms of these include the furnace continuously 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 solved by HVAC pros like the team at AZ Air Conditioning and Heating.