Why Does My Heater Blow Hot Air Then Cold Air?

by | Last updated on January 24, 2024

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If your starts blowing warm but then quickly turns cold, the

flame sensor

may need attention. A flame sensor that's covered with grime or worn out can cause the burner to keep shutting off. You'll need a visit from an HVAC professional to make this furnace repair.

Why does my heater blow cold air then hot?

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.

Why is cool air coming from the vents even though heat is on?


Clogged air filters could be causing cold air to blow

out of your vents. A dirty air filter can block airflow over your furnace's heat exchanger, which can cause it to overheat.

What do I do if my heater is blowing cold air?

When your furnace blows cold air, try

turning the heating unit off and on

. If the air feels warm for a moment or two, then switches to cold, it may be that the flame sensor is dirty. With a dirty flame sensor, your gas burner won't stay lit, causing the air to go cold soon after the furnace turns on.

What to check if heat is not working?

Check your power source—a tripped circuit breaker or blown fuse could be the reason for your furnace failure. Reset your breaker or replace the fuse to see if that restores heat.

Check your filter

—if it's so dirty that your system is struggling to move air through it, your furnace could overheat and shut down.

Why is my furnace running but not blowing hot air?

Furnace overheating can be the cause of your cold air dilemma.

Changing the dirty air filter

can solve this problem. The dirty air filter blocks the airflow, causing the furnace to run longer to heat your home until it overheats. It is important to note that constant overheating can damage your heat exchanger.

How do I stop my heat pump from blowing out cold air?

  1. Turn off the heat at the thermostat and check your air filter. If it's dirty, change it!
  2. Make sure the thermostat is set to “AUTO”, not “ON”. When set to “ON” the fan will stay on even when your heat pump isn't actually heating.

Why is my furnace running but no heat?

Furnace filters

Dirty filters are the most common cause of furnace problems. Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won't warm up. If the blower is running but no heat is coming out,

replace the filter

.

What does it mean when your heat is blowing out cold air in your car?

A car heating system blowing cold air can be due to a

faulty thermostat

, low coolant fluid level, malfunctioning heater core, a leaking cooling system, or problems with heating controls and blend door.

Is there a fan that blows cold air?


NewAir

Fan that Blows Cold Air

This is another cold fan that essentially operates like a swamp cooler: it uses water to cool down the air that passes through it. … The NewAir AF-310 Portable Evaporative Cooler Fan can lower the temperature in a room by 15 degrees!

How do you know if your heat is on?

Once you feel hot air coming through your vents,

walk outside and see if the outdoor unit is running

. You see, a heat pump is an air conditioner that can also provide heat during the winter. So if the outside unit is running and producing heat, then you have a heat pump.

How do I reset my heating system?

  1. First, turn off the power supply to the furnace by turning off the breaker in the circuit box.
  2. Locate the reset button on the furnace and press it to reset the furnace. …
  3. If the button is popped up, press it down.
  4. Return the cover to the blower compartment and turn the power on.

How do I check my heating system?

  1. Turn off your programmer/boiler and turn your room thermostat down to 0, if you have one, if not use the thermostat on your boiler.
  2. Turn on your boiler/programmer and central heating, making sure your hot water is turned off.

What temperature should the hot air be coming out of the vent?

The air coming out should be

14 to 20 degrees cooler than the air flowing in

. Move the thermometer to a vent in each room or area of your home. If any of the vents are much colder or warmer than another, there may be a problem with the ductwork, or the distance may be too great from the blower.

At what temperature do heat pumps become ineffective?

Heat pumps do not operate as efficiently when temperatures drop to

between 25 and 40 degrees Fahrenheit

for most systems. A heat pump works best when the temperature is above 40. Once outdoor temperatures drop to 40 degrees, heat pumps start losing efficiency, and they consume more energy to do their jobs.

How do I know if my heat pump is working properly?

The main way to tell if your system is working as intended is to

simply listen to the unit running

. You can hear the system when it turns on, when the fans begin to work and stop, and when air passes through the ducts. Other than that, the unit itself should be quiet, without any groaning or creaking sounds.

David Martineau
Author
David Martineau
David is an interior designer and home improvement expert. With a degree in architecture, David has worked on various renovation projects and has written for several home and garden publications. David's expertise in decorating, renovation, and repair will help you create your dream home.