Fixing a heating system that blows cold air requires systematic troubleshooting based on the specific type of equipment and operational symptoms. If you have a heat pump, check if the outdoor unit is locked in a defrost cycle or if the reversing valve is stuck, which can be diagnosed by a professional technician. If you have a gas furnace, cold air blowing usually indicates that the burners failed to ignite due to a bad igniter, a dirty flame sensor, or a tripped safety switch, causing the blower fan to circulate unheated room air. You can start by checking your thermostat settings, replacing a dirty air filter, and ensuring gas or electrical breakers are turned on. You can verify that your troubleshooting steps were successful when the system ignites properly and warm air flows steadily from your indoor supply registers.
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