A clogged air filter restricts airflow, significantly reducing the efficiency of your furnace and possibly leading to it blowing cold air. Locate the filter, which is typically found in the return air duct or blower compartment. Turn off the furnace before removing the filter to examine it.
Your furnace may be blowing cold air because the filter is too dirty. A dirty air filter blocks airflow over the furnace's heat exchanger, causing it to overheat. When overheating, your furnace can trip a high limit switch, causing the furnace burners to shut off so that the heat exchanger does not crack.
The most common issues include a faulty thermostat but these issues could also be a sign of a clogged filter, dirty air ducts, or a serious problem with your furnace.
You shouldn't turn off your furnace just set the thermostat so the furnace will only come on if the temperature drops around 50F 10Celsius. On thermostats that run both the heater and AC, make sure the system is switched over to ``cool'' and the furnace won't turn on.
First, turn off the power supply to the furnace by turning off the breaker in the circuit box. Locate the reset button on the furnace and press it to reset the furnace. It is usually located inside the blower compartment on the side of the blower motor. Be cautious, as the housing may be hot.
Carrier furnaces typically have a small reset button inside the burner compartment. It may be red or yellow and is usually labeled “Reset.” If you're unsure where to find it, consult your furnace's user manual. Hold the button down for about 10 seconds before releasing it.
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.
If your furnace is blowing cold air in your home, this is a sign of an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. Many of these issues are able to be easily solved on your own by sanitizing or replacing components in the gas furnace.
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.
Airflow Temperature Vs. Thermostat Temperature. Hot air leaving the furnace burner is generally between 140 and 170 degrees Fahrenheit. By the time the airflow passes through the ductwork and enters a room at the supply vent, the temperature has typically dropped to about 120 to 140 degrees.
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.
Choose "AUTO" for energy savings and "ON" if you want constant air circulation or improved air filtration. Temperatures can soar or plummet depending on the time of year. Throughout the year, it is important to have reliable heating and cooling systems in order to keep your home supplied with cool or warm air.
Leaky Air Ducts
Your heater might also be blowing cold air because of leaky ducts. Leaks in your ductwork can cause warm air to escape before it reaches your rooms, causing cool air to come through the vents. A leak can occur because of poor insulation, aging ducts, or damage.
A clogged air filter restricts airflow, significantly reducing the efficiency of your furnace and possibly leading to it blowing cold air. Locate the filter, which is typically found in the return air duct or blower compartment. Turn off the furnace before removing the filter to examine it.
An electric heater that blows cold air could be caused by one or more of the following reasons: The manual reset has tripped. The fan switch is “on” and the thermostat setting is below the actual temperature. The fan is dispersing this air after shutdown.
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.
Typically, there's a 10 to 15 minutes allowance for this. However, if after this time it's still producing cold air, then there's an underlying problem that needs to be addressed. It would be wise to turn the furnace off and get in touch with a pro immediately for help dealing with the issue.
When the thermostat can't signal that the engine is warm, the coolant won't be sent over to provide heat to the heater core and the air will blow cold. Solution: You need to install a new thermostat to get your heater working again. It's a relatively quick and easy fix.
If your furnace is malfunctioning or not turning on, we recommend troubleshooting it by checking and replacing the air filter. If the issue persists, you may need to call an HVAC technician for further testing. To ensure your furnace filter stays clog-free, remember to replace or clean it every three months.
Wait 5 to 10 Minutes
Once you've turned off both the power and the circuit breaker, wait a few minutes before turning anything back on. This allows the furnace's internal systems to fully reset and clear any error messages or lockout modes.