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 affect your home at any moment.

Regardless of the cause, learning how your heating system works and a little bit about some common furnace problems is crucial in deciding whether you can troubleshoot on your own or if you need professional assistance. By noting 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 Mechanical Air Systems Co. We can accurately diagnose the issue and execute 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 frequent heating issues:

1. The Furnace Is Leaking

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

It is necessary to address water leaks immediately to prevent further damage to your furnace. Consulting with a professional HVAC technician like the crew at Mechanical Air Systems Co is recommended to diagnose and resolve the issue properly.

2. My Furnace Is Blowing Cold Air/Lack of Heat

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

If your furnace does not blow hot air, it's best to contact a skilled HVAC technician to diagnose and fix the problem. They can give an accurate assessment and advise you on the appropriate solution.

3. My Furnace Can't Keep Up

A frequent reason your furnace isn’t keeping up on a cold day is that your home is lacking insulation, which can result in 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 adequately warm the space. A defective thermostat or ductwork problems can also result in insufficient heating.

To address this, first assess your home’s insulation level and make sure it’s enough to protect your home. Also, examine 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 Mechanical Air Systems Co, 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 couple of steps you can take to troubleshoot before phoning a professional. Ensure the thermostat is set correctly 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 furnace.

If there is power but your furnace won't ignite, the problem may be with the ignition system or gas supply. In that case, it's better to reach out to an experienced 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 is designed to do. This can lead to inefficiency, increased energy consumption and potential damage to your unit.

If you believe your furnace is short cycling, the first step is to pull out your unit’s air filter. Filters should be exchanged on a regular basis to ensure air flow, so if your furnace air filter is dirty you should exchange it for a clean one—and make sure it is pointing in the right direction. Next, look at your thermostat and make sure  it’s set right and the batteries are good.

If those two things don’t work, it’s smart to call experts like the team at Mechanical Air Systems Co. Prompt professional attention will help restore the proper functioning of your furnace and reduce the chance of further complications and high energy bills.

6. My Furnace Is Making a Humming Noise

When your furnace is making a humming noise, it often is an indication of problems with the electrical hardware or the blower motor. Therefore, if you detect your furnace making a humming noise, it is critical to take action.

If the noise persists, it is best to  contact 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 address the issue right away to prevent further damage or potential safety risks.  One common problem that causes 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 emit a squealing or rattling noise.

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

8. My Furnace Won't Start

If your furnace refuses to turn on, make sure the thermostat is set to the right temperature, is in heating mode and the batteries are functioning. Then, verify that the circuit breaker or fuse that controls the furnace is working right. 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 work, call an expert for furnace repair.

9. My Furnace Won't Ignite

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

Other likely causes of a furnace not igniting include a faulty igniter or malfunctioning flame sensor. Signs of these include the furnace continuously trying to ignite without success, no heat production or the furnace is making a burning or gas smell. Both of these issues can be simply fixed by HVAC specialists like the team at Mechanical Air Systems Co.