Furnaces are amazing machines that run and stop all the time, so the risk for malfunctioning is never null. Sometimes, the problems are minor and request an easy fix, whereas other times, you will have to call the HVAC professional for troubleshooting and repairs.
Should you realize that you have a furnace running but not blowing air, the situation’s problems are numerous and various. Either way, you have to check it and try to solve the problem as it never goes away on its own. Scroll down for the details.
Page Table of Contents
- 1. Does it have power?
- 2. The furnace isn’t in “heat mode”
- 3. Is the temperature set correctly?
- 4. The thermostat isn’t properly mounted
- 5. The date and time are wrong
- 6. The filter could be clogged
- 7. The Circuit Breaker Is damaged
- 8. The blower fan doesn’t work
- 6. The limit control switch is damaged
- 7. The heating coils don’t run
- What can you do when the furnace isn’t blowing air?
1. Does it have power?
It’s quite common for furnaces to trip breakers and blow fuses, especially if some underlying problems or factors lead to an overload. Most of the time, the furnace is the only device on the circuit, so it’s the only appliance affected. You have to check if there’s power or not before anything else.
2. The furnace isn’t in “heat mode”
Regardless of what you may think, it’s common for homeowners to activate the furnace while leaving the thermostat in air conditioning mode and not set it to “heat mode.” Many people forget about the setting option and don’t even suspect what could be wrong. Thermostats today come with numerous features and are rather tricky to set. They provide so many options that people get confused and misprogram the furnace.
3. Is the temperature set correctly?
In a household with several people living, there could be some differences in what comfortable temperature means. For one, “warm” could be “chilly” for another person. Therefore, the thermostat could be turned down at some point, without the other occupants of the house knowing it.
You should look at the temperature setting to see that it’s the temp you want, especially if you don’t feel it’s warm enough in the house.
4. The thermostat isn’t properly mounted
If you’ve recently mounted a thermostat on your own, you may have missed some steps throughout the process. Thermostats and furnaces are sophisticated devices, and even if you’ve followed the steps accurately, you can still miss some slight adjustments. Only HVAC technicians can make some of these adjustments.
It’s also possible that the new thermostat doesn’t match your furnace. The market provides an impressive selection of models, but they’re not all compatible with the furnace you have at home.
5. The date and time are wrong
As you can see, many of the problems with a furnace not blowing air or blowing cold air instead of hot air have to do with the thermostat. Some of these issues are relatively simple yet important enough to cause improper functioning of the furnace.
Sometimes, the date and time aren’t set right on the thermostat, causing the problem. Many homeowners aren’t even aware that their programmable thermostats have the date and time settings off.
Programmable thermostats are great as you may set them when to give hot air. But if it’s 6 pm and your thermostat has time off and thinks it’s 1 pm, it’s probably why you don’t have hot air in your home.
The time and date could be off because the batteries on the thermostat are dead. Without battery power, it’s understandable why the thermostat will reset after a brownout or blackout. Always check the batteries on your thermostat and set the date and time correctly.
6. The filter could be clogged
Two problems can cause the clogged filter: it can block airflow and may affect tripped shutoff functions. Sometimes, the debris and dust buildup is so thick that it doesn’t allow the hot air to pass through the filter anymore. Even if the furnace is running, the hot air doesn’t pass through the filter per se. You will have to replace the filter, most of the time.
Clogged furnace filters can also push the furnace to work harder, causing overheating and activation of the automatic safety shutoff. Even if you think that the furnace is still running, it has overheated and stopped because of the clogged air filter.
7. The Circuit Breaker Is damaged
Modern and complicated furnaces today come with circuit breakers. A heating system may come with two, and even three circuit breakers, and any of them can trip and make the furnace stopped. When a circuit breaker is off, the furnace won’t heat anymore. If the circuit breaker to the blower fan is out, the heating coils won’t spread the heat anymore.
Keep in mind that you can only test a circuit breaker once. Should it trip several times, you have to call the HVAC technician for further investigations.
8. The blower fan doesn’t work
When your furnace is running, but it doesn’t blow air (no matter if it’s cold, warm, or hot air), and you’ve ruled out the thermostat, air filters, and circuit breakers, the blower fan could cause the problem.
The blower fan is supposed to blow air over the furnace’s heating coils, spreading the warmth throughout the air ducts. When the blower fan doesn’t run anymore, the problem is rather tricky to solve.
You may check the blower fan, turn the heat off, and switch the fan from “auto” to “on.” You have to give it a couple of minutes to see if any air comes out or not.
6. The limit control switch is damaged
The limit control switch (some know it as the fan limit switch or the furnace fan control switch) monitors the fan and heating coils’ automatic on/off functions. When the furnace is turned off, or your room is pleasantly warm, the furnace stops automatically, and it’s the control switch turning the blower off for saving energy.
When the heating coils heat the air, the control switch will push the blowers to spread the heat throughout the house and the ducts.
When the furnace isn’t blowing air, the limit control switch may be the culprit. Should your furnace overheat, the control switch shuts off the system for safety reasons. A misreading from the limit control switch or overheating could cause the shutoff. If that’s not the case, the limit control switch could be damaged, which isn’t excellent news.
7. The heating coils don’t run
Even if the blower fan not working isn’t a minor problem, heating coils not working is even worse. When the heating coils aren’t running, no thermostat settings, clean filters, or switch fixes will make your furnace blow air. When all the possible causes have been ruled out and replaced the limit control switch, the heating coils cause the furnace not to blow air.
What can you do when the furnace isn’t blowing air?
You can take several steps to identify the cause for your furnace, not blowing air. If the issue is minor, you can probably fix it on your own. However, you will have to call the HVAC technician for more severe problems. Here are the fixes you can try:
1. Take a look at the thermostat
Don’t call the HVAC professional until you’ve checked the thermostat. Make sure that the settings, modes, and levels are the way you want. Also, ensure that your thermostat isn’t set to “cool” but on “heat.”
Increase the thermostat temperature by five degrees, waiting for the system to run; it’s an excellent way to test the heat quality. Is the air hot? Please take a look at the batteries and replace them with new ones. Don’t forget to remove any dust from under the thermostat panel, too; it can affect adequately functioning.
2. Observe the Air Filter
The air filter is relatively easy to examine, as it’s not difficult to see if the filter is clogged and blocks air from circulating. To some extent, the air filter acts like the lint trap in your laundry dryer, as you have to clear it between every usage cycle.
Check the air filter every three months and replace it if the dirt buildup is beyond cleaning. Needless to say, always shut off the furnace and thermostat before checking the air filter.
3. Verify the Gas Supply
Should you have a gas furnace, you also have to make sure that the fuel supply is enough. Take a look at the gas valve and see if it’s set to “on.” Sometimes, the gas valve remains off after some maintenance or easy fixes.
If you suspect a gas leak, you should immediately turn off the gas valve and every switch on the heating system. Call the gas company and don’t light any lighters or matches close to the furnace. Get out of the house immediately and wait for the gas company’s people to solve the problem.
4. Take a look at the Pilot Light
Pilot lights are standard for the older models of gas furnaces. When the pilot light isn’t capable of staying lit, a clogged orifice may cause the problem. Use a tiny piece of wire for poking it clear, but only after turning off the furnace and the circuit breaker.
A weak flame setting, a faulty cutoff valve, or a loose thermocouple could cause a defective pilot light. These are problems that only the HVAC professional should address.
5. Call the professionals
Even if the minor furnace problems come with simple fixes, many of the issues related to your furnace are best solved by professionals. Keep the HVAC technician’s contact number close to the furnace; you never know when you’re going to need it.