Whether it’s a leaky furnace or if you flip the switch to power up 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 cause, 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 assistance. 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 unsure about the problem or don't have 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 ready to go 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 created during the combustion process is not effectively draining away. This could be due to a blocked condensate drain line or a malfunctioning condensate pump. Another potential cause of water leakage from a furnace is a cracked heat exchanger, which can lead to water—as well as dangerous gases—escaping from the furnace.

It is imperative to correct water leaks quickly to prevent further damage to your furnace. Reaching out to 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/Lack of Heat

Some potential 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 plugged air filter, or a malfunctioning heating element. It could also be your furnace is overheating and shutting off as a safety measure.

If your furnace won’t blow hot air, it's a good idea to contact a trained HVAC tech to diagnose and fix the problem. They can give an accurate assessment and advise you on the appropriate 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 cause 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 produce enough heat to effectively warm the space. A broken thermostat or ductwork problems can also produce uneven heating.

To correct this, first check your home’s insulation level and make sure it’s enough to protect your home. Also, check the thermostat to see if it’s set right and the batteries still function.

If the problem lingers, consider calling an experienced HVAC company, such as AZ Air Conditioning and Heating, 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 Isn't Running at All

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

If there is power but your furnace won't ignite, the problem may lie with the ignition system or gas supply. In that case, it's better to contact a seasoned 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 multiple times at short intervals instead of running in regular cycles like it is designed to do. This can lead to inefficiency, more energy use and potential damage to your unit.

If you believe your furnace is short cycling, the first step is to check your unit’s air filter. Filters should be switched out on a regular basis 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, go to your thermostat and verify  it’s set right and the batteries are good.

If those two things don’t work, it’s best to call experts like the staff at AZ Air Conditioning and Heating. Prompt professional attention will help restore the proper functioning of your furnace and reduce the chance of more complications and high energy bills.

6. My Furnace Is Making a Humming Noise

When your furnace is making a humming noise, it often is a symptom of an issue with the electrical parts or the blower motor. Because of this, if you detect 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 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 risks.  One common cause of this is a failing blower motor or fan, which can make a grinding or screeching sound. Another possible cause is a loose or worn-out belt that may make a squealing or rattling noise.

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

8. My Furnace Can't Turn On

If your furnace won't turn on, make sure the thermostat is set to the right temperature, is in heating mode and the batteries are working. Then, verify that the circuit breaker or fuse that goes to the furnace is functioning properly. If these basic checks don't resolve the problem, you can check 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, call a heating specialist for furnace repair.

9. My Furnace Is on but Not Igniting

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

Other likely causes of a furnace not igniting could be a faulty igniter or malfunctioning flame sensor. Symptoms of these include the furnace repeatedly making an attempt to ignite without success, an absence of heat production or the furnace is making a burning or gas smell. Both of these issues can be simply repaired by HVAC pros like the team at AZ Air Conditioning and Heating.