It can sound like the furnace itself is running, but it's just the blower motor. When the motor runs alone,
Most likely, your furnace is making a clicking noise and not providing heat because your furnace's spark igniter is trying to ignite your pilot light or burners but is failing to do so. In other words, there's an ignition system malfunction that needs to be fixed.
In this article, we discuss three of the most common reasons why a furnace turns on without generating heat. These include incorrect thermostat settings, airflow problems, inadequate furnace fuel, and ignition problems.
Check Furnace Thermostat Settings
Incorrect thermostat settings can be the cause behind no heat coming out of the vents, even with the furnace blower turned on. Check the thermostat to ensure the setting is in HEAT instead of COOL. It is a common mistake that happens. The fan runs continuously when it is switched on.
Loud Bangs, Rumbles, Knocks, or Booms
Loud noises like this are a sign of a build of gas in a furnace. The noise you hear can mean your heat exchanger is at risk of cracking. Even worse, it's a sign that something dangerous could happen if you continue to use your heater.
In most cases, these noises come from newer, high-efficiency furnaces. The high-efficiency furnaces vent exhaust fumes may produce condensation from moisture in the air that must be drained. When there's an issue in draining this condensation, it may cause gurgling, dripping, or other watery sounds.
Make sure your thermostat is set to “heat” and the temperature is high enough to turn on the furnace. Go to your electrical panel and check the circuit breaker. If it's tripped, reset it and turn the furnace back on. Check your furnace filter and if it's dirty replace it with a new one.
If your furnace is blowing hot but your home is still cold, it may be a problem with your ductwork. You may have leaky or damaged ducts that are letting hot air escape and cold air in. Sometimes a damper in the system can get miss-adjusted or come loose, thereby inadvertently blocking or reducing airflow.
Possible reasons include thermostat issues (incorrect settings or dead batteries), power problems (tripped circuit breaker or blown fuse), and furnace malfunctions (dirty air filter, faulty ignition system, or tripped safety switches). Checking these areas can help identify the issue.
If the thermostat clicks but the AC or furnace doesn't turn on, most often it's because the filter is clogged. A blocked filter will restrict airflow. The particles it's designed to trap eventually clog the filter media, and the system will be unable to generate heat or cool air.
Ensure your thermostat has not been set to a lower setting by someone else. Check your thermostat's batteries and replace any that are exhausted or defective. Clean all of the parts of your furnace, especially the ones that are susceptible to dust and dirt.
In most newer systems, the button is often directly next to the blower motor, while in older systems, it may be harder to spot as it is sometimes underneath or behind the motor. The reset button is often made of yellow or red plastic and marked with a large “R ” to make it easier to spot.
You Have Cold Air Blowing Out The Vents When The Heat Is On Because of a Dirty Air Filter. Hiding in the filter of your heating system is dirt and debris. If you aren't cleaning it regularly, this will accumulate over time, leading to problems with your heating system's efficiency.
Furnace is not producing enough heat.
This may be caused by obstructed airflow or dirty or misaligned gas burners. In some cases, airflow is obstructed by a dirty furnace air filter, and if it is replaced, the problem is solved.
If your thermostat won't turn on the heat in your home, change out the batteries and see if that fixes the problem. If not, your faulty thermostat could be the result of the following: A tripped breaker. Loose wiring.
When you turn the furnace on but no heat comes out, there may be an obstruction. Dirty air filters restrict airflow, which can make it feel like not much heated air is coming out of your vents. Check the furnace filter and replace it if its surface is covered with contaminants.
Defective Igniter or Pilot Light
If it makes a clicking noise but your furnace won't ignite after its combustion cycle, then it's more than likely going to need to replace the electronic ignition systems.
A loose transformer box.
If the mount of the transformer comes loose, it may produce a buzzing noise as the furnace starts up. A loose transformer box is commonly to blame when the furnace has been recently installed. On older furnaces, a buzzing or loud humming noise likely means the transformer needs to be replaced.
When a furnace starts up to run a heating cycle, most homeowners notice some noise. This noise is typically not something to worry about. The main reason you notice it is because it wasn't on a moment ago!