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.
If your thermostat is off but heat is still on, you are probably experiencing some kind of "short" or connection issue. Most often with this problem is that a wire is touching something it should not be touching. Another possibility is that the gas valve is stuck open. This is rare, but it can happen. If.
If your furnace turns on but no heat is produced, there may be a problem with the fuel supply or the ignition system. If something is stopping your furnace from receiving gas, there is no fuel to combust so the furnace will not create any heat. The furnace turns on but no heat comes out.
The first thing to check is the filters in the return air duct(s). This might be at the furnace or they could be at the return air grilles. Next thing to check is to see if the evaporator (cooling) coil in the furnace ductwork is frozen. These are the two primary causes of no airflow from the registers.
Obstructed Vent
Furniture, bedding, and the vent damper could all be possible obstacles to the vent. If you find any closed or blocked vents, you can clear away the obstruction and feel for airflow, but if your vents are open and still not blowing enough air, there could be an issue with the fan's motor.
There are several reasons why your furnace may not turn on. The most common include a broken thermostat, gas line issues, clogged air filters, blocked ductwork, a tripped circuit breaker, and issues with the furnace itself.
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. Otherwise, your furnace won't start.
Checking your thermostat is the best place to start. Make sure it's set to “heat” and that you've set the temperature higher than the current room temperature. If that doesn't resolve the problem, try switching your fan to “on” to force the furnace to start working.
It's most likely an incorrect thermostat setting if you find your furnace blowing warm air, not hot. The fan is set to “on” instead of “auto.” Furnaces only pump hot air until the thermostat setting is reached, so if your fan is always on, it will blow both hot air when the furnace is heating and cold when it's not.
If nothing's happening when you're expecting the whir of a blower, check the circuit breaker and fuse. At your electrical panel, make sure all switches related to the HVAC system are on. Reset any tripped breakers and replace all blown fuses, and your furnace should kick back on.
This can occur if there's a malfunction in the furnace's components, such as a faulty limit switch or a blocked heat exchanger. In such cases, it's crucial to consult a professional HVAC technician for a thorough inspection and necessary repairs.
Try checking the circuit breaker box or replacing the batteries. Bad wiring: The thermostat may be unresponsive if the wiring has gone bad. Remove the cover and check inside for loose, detached, or corroded wires. If you spot any problems, contact an HVAC technician for assistance.
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.
Check the pilot ignition light.
(Electronic ignitions will not have a pilot light.) If your furnace clicks on or initiates the start cycle, but does not fire up, you likely have a faulty or dirty ignitor/sensor. This is one of the most common furnace problems.
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.
If your gas furnace initiates the start cycle but doesn't fire up, it's likely because of a faulty, damaged, or dirty ignitor/sensor. This is a very common problem — you can try to clean the sensor and replace the ignitor.
When your furnace runs but fails to blow air, several issues could be at play: Blower Motor Problems: If the motor is malfunctioning or not receiving power, it can't push air through your ducts. This could be due to electrical issues, a faulty motor, or problems with the motor's capacitor.
While furnaces can stop operating for complicated reasons, home owners should check a few usual suspects first behind a lack of hot blowing air: Electrical problems causing a loss of power. Blocked air vents and ducts restricting airflow. Improperly configured thermostat settings.
The electrical wiring within the boiler may have come loose, the programming within the boiler may have malfunctioned, the cylinder thermostat may need replacing, the fan may have stopped working, the pump may have broken… The list of potential problems is almost endless.
If your heater doesn't start, chances are the problem stems from having a dirty furnace. Having dirt on your blower motor or flamer sensor could render your furnace unable to perform. When the blower motor is too dirty, it won't pass enough cool air to the heat exchanger, leading to equipment failure.
Defective Igniter or Pilot Light
If it clicks but your furnace won't ignite after the combustion cycle, the electronic ignition systems probably need to be replaced. In cases where the furnace ignition starts normally but only stays on for a few minutes and then goes out, a new pilot light likely needs to be installed.
Check Thermostat Settings: Ensure the thermostat is set to “heat,” and the fan is on “auto.” Inspect Air Filter: Replace a dirty or clogged air filter with a new one. Relight the Pilot: If you have a pilot light, follow the manufacturer's instructions to relight it.