Furnace Not Blowing Hot Air: Guide to Troubleshooting Common Furnace Issues

By January 20, 2020Blog
furnace not blowing hot air

In the United States, over 80% of homes use either gas or electric furnaces. While most modern heating and cooling systems are reliable, eventually you’ll have a problem with yours.

What do you do if your furnace is not blowing hot air? The process that you’ll have to go through is called troubleshooting. Troubleshooting will help you figure out what is wrong with your furnace.

Finding out what’s wrong with your furnace can help the repair process go much smoother.

Basics of a Furnace Not Blowing Hot Air

Furnaces are simple in concept. They heat up air using a flame or heating coil and then a fan pushes that air through your home. This is why you hear the term “forced-air” associated with heaters. Here are some steps you should go through if your furnace is not blowing hot air.

1. The Furnace Is Blowing Cold Air

First, check to make sure the thermostat is set correctly. You will want to make sure that the fan control is set to auto, and not ‘on’. If the thermostat appears set correctly, turn off your heater at the thermostat and check the filter.

If the filter is dirty, replace it. If the filter is not dirty, move on to the furnace itself. If you have an older furnace you can check the pilot light. For a newer furnace, it will use an electric ignition instead.

At this point, you can try to relight the pilot light. On an older furnace, you do this by finding the dial that has “on”, “off” and “light” on it. Turn the furnace off for about five minutes then turn it to light and push in the button.

Use an extended lighter to try and turn the pilot back on. If your pilot lights, turn the knob back to “on” and leave it. If this doesn’t work, or if you have a modern unit, you should contact a professional HVAC repairman to check your problem out.

2.  Furnace Is Not Turning On 

Always check to make sure the thermostat is on and that the filter is clean. These are the first two steps to any problem you might have.

After you check the thermostat and filter, go to your electrical box. If you don’t feel comfortable checking to see if a fuse has been tripped, contact a professional. If you find nothing wrong, head down to the furnace.

Make sure the furnace is turned on. It is possible that the switch got flipped and the furnace is off. If this is the case, turn the furnace back on. If the furnace has power, then open the side of the furnace up.

Some furnaces will have a reset switch that may have got flipped. If they do, research your model and try to hit the reset button. If that doesn’t work, you will have to contact a professional repair person in order to get deeper into your problem.

3. Common Heater Problems

Furnaces as they age will all eventually have problems. Regular maintenance is vital to make sure that these problems don’t appear until way further down the line.

The most common problems with furnaces deal with thermostats that don’t work correctly and filters. Filters must be replaced often in order for the furnace to operate properly. If you don’t, you are making your furnace work much harder.

Your furnace could have a cracked heat exchanger. This is the kind of fix that you should definitely get a professional to look at.

If the furnace makes loud noises you could have a clogged burner, airflow problem, or worn-out ball bearings in your unit. For cases such as this, a professional should be called in to fix the problem.

If that loud noise is a high-pitched squeal, it could be because you have a problem with a belt. The belt which runs the fan can become frayed just like in a car. It can even make the same squeal you hear from some older vehicles.

If your furnace cycles a lot between on and off, check the filter. These conditions are most often caused by thermostats and filters. Make sure that airflow into your furnace is not blocked or limited.

If the furnace heats up just fine but continuously blows even when it is not putting out warm air there can be a problem with your limit switch. Swapping out the limit switch should only be done by someone who knows what they are doing.

If your furnace does not heat up enough you might have an ignition or pilot issue. Often a lot of these problems can be caught before they become serious if you have an HVAC tune-up in the fall.

Don’t Do Anything You’re Uncomfortable With

When it comes to repairing any major appliance, and especially your HVAC system, be careful. These units use a lot of electricity and gas and can be dangerous.

If you are unsure of yourself or don’t know how to address a problem, don’t feel bad about contacting an HVAC repair person. They are trained and equipped to deal with problems in your HVAC system.

If you’re going to check a fuse box or anything to do with the electrical system, make sure your hands are dry. Never touch any exposed wiring and if there is anything you feel uncomfortable about, stop what you’re doing immediately.

HVAC Repair You Can Trust

While most problems are fairly easy to deal with, even those can be a big hassle without the proper knowledge. Contacting an HVAC repair person is usually the best idea to deal with furnace issues.

Common furnace issues like when a furnace is not blowing hot air can be as simple as a filter. New furnaces cost on average over $3,000. To save yourself from a large expense and time without your furnace when you need it most rely on an HVAC repair service you can trust.

Contact us at Guys Air Conditioning and Heating service to get back up and running.