My Central Heat & Air With Gas Heat Is Only Blowing Cold Air: Why?


On a cold day there is nothing like feeling the blast of warm air from your heater to help you shake off the miserable chill. But if your central gas heating system is blowing only cold air, it can have the opposite effect and intensify the misery. There is obviously a problem with the system somewhere if you feel chilly air coming from the registers. You’ll need to start with the most obvious problems and work your way through the system to figured it out so you can return to a cozy feeling in your home.


  • A central air conditioning and heating system can perform several different functions. It can heat your rooms in winter, cool them off in summer and circulate air to keep the temperatures even throughout the home. Whether it is heating, cooling or just blowing room-temperature air is determined by the thermostat settings. Check the thermostat to see if you have it set to the proper function. Make sure the heater switch is set to “heat” and not “fan” or “cool.” The fan setting will only blow around the cold air you already have, and the cool setting will make it colder. This is a simple and common mistake and you can fix it yourself in just a couple of seconds. You should also make sure you have the thermostat temperature setting raised to a level higher than the current room temperature.

Gas Supply

  • Since your system heats using natural gas or propane, you will have to make sure you have a gas supply. Ensure the gas main to the appliance is turned on. If you have a propane tank outside your home, make sure it has propane in it. The burners will not light without this gas for fuel.

Pilot Light

  • Some central gas furnaces use a pilot light that remains lit at all times during the heating season. The flame from the small pilot ignites the burners when the flow of gas arrives to begin heating. If the pilot goes out, then the gas will simply fill the combustion chamber and no heat will result. You will typically smell gas when this happens because it will begin to build up in the system. Do not try to light it manually while the gas is on. Let it ventilate completely and then follow instructions to relight the pilot, or call your gas company to have a professional do it for you.


  • Some gas heating systems use an igniter instead of a pilot light. If yours has an igniter, it will heat up when the gas is turned on and ignite the gas burners after the gas is on for a few seconds. If the igniter is faulty, it will not light the burners and the result will be the same as if a pilot light had gone out. You may need to replace the igniter if this problem persists.

Give It Time

  • In some instances, the fan on your central unit may begin blowing immediately, even before the burners light and heat up. The cold air in the ducts will blow out as the fan kicks on, but the heated air will follow within a few seconds. Simply give it time and see if the problem corrects itself.

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