A dirty or clogged air filter can restrict airflow, causing your furnace to overheat and shut off the burners. In such cases, the blower fan will continue running, but no warm air will be distributed throughout your home.
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.
A variety of factors can cause short cycling: a clogged air filter, a malfunctioning thermostat, a faulty limit switch, overheating, or a problem with the furnace's heat exchanger. Since short cycling is both a symptom of another problem and a problem in itself, have technicians look into it ASAP.
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.
If your thermostat is fully functional and you're still unable to feel any heat coming from the vents, you may be dealing with some of these problems: Dirty evaporator coils. Clogged pipes. Full air filters.
The first step in diagnosing the issue is to check your thermostat settings. Ensure that it's set to “Heat” mode and the desired temperature is higher than the current room temperature. Sometimes, the thermostat might be accidentally set to “Cool” or “Fan Only,” causing the furnace to run without heating.
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.
Check your home's circuit breaker or fuse box for any tripped breakers or blown fuses. Also, ensure that the furnace's power switch, usually located on or near the unit, is turned on. Inspect Vents and Registers: Ensure all vents and registers in your home are open and unobstructed.
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.
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.
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.
A dirty air filter, a faulty thermostat, a faulty pilot light, or a problem with the ignition system are all possible causes. It's also possible that your boiler needs to be more powerful to heat your home adequately.
A furnace blowing cold air could be the result of a leak in your ducting. Over time, the changing temperatures wear on all sorts of things, including your ductwork. In fact, it's rather normal for ductwork to develop leaks over time. When ductwork has a leak, cold air will enter a duct and blow into your home.
If your furnace is not blowing hot air, or is not operating at all, a component called the fan limit switch or high limit switch may have malfunctioned. You may also see an error message on your thermostat, or a blinking LED light on the furnace control board.
The thermostat may have a dead battery, so replace them with fresh ones and try again. Your furnace may turn on right away after this. If it doesn't, you may have a faulty power circuit. Have an HVAC professional diagnose this issue, and provide you with professional recommendations.
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 most common reason a heat pump is blowing cold air through your air vents is defrost mode. This is a safety feature to melt frost and ice within the system. During defrost mode your heat pump made switch modes to heat up the outdoor coils. Indoor temperatures will fall because the system is briefly in cooling mode.
It needs to be set to heat mode – if it has been accidentally set to cool, you get no heat. Also, check the fan settings, as errors here often produce a situation where the heating system appears to be running, but only cold air comes from vents.
What should I do?” Check these places first, check if your air filter is dirty, if your thermostat is set correctly or if you need to change your thermostat battery! The air coming out of your vents might feel cold when the furnace first kicks on, but it should warm up fairly quickly.
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.
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.