Why Your Furnace Is Blowing Cold Air in Dallas (And How to Fix It)

If your furnace is blowing cold air, check three things first: thermostat settings, air filter, and furnace door. These cover 80% of cold air issues and take less than 5 minutes to inspect. This guide from Dallas Heating and Air Conditioning walks you through DIY fixes and when to call for professional furnace repair.

Quick Checks You Can Do Right Now

Start with the thermostat fan setting. When set to "On," the blower runs continuously and circulates unheated air between heating cycles. This feels like cold air but isn't a malfunction.

Problems That Need Professional Repair

Pilot Light or Igniter Failure

Your furnace can't light the burners, so the blower runs but produces no heat. Modern furnaces use hot surface igniters that glow orange when working. You'll hear the furnace attempt to start, maybe clicking sounds, but no ignition occurs.

Igniter replacement requires furnace access and handling gas system components. In North Texas, dust accumulates on igniters during the 8-9 months furnaces sit idle, making startup failures common in November. Professional repair costs $150-$300.

Dirty or Faulty Flame Sensor

The flame sensor detects whether burners are lit. When dirty, it can't detect the flame properly, so your furnace shuts off as a safety precaution. Burners light briefly, then shut off after 3-10 seconds. This cycle repeats continuously.

Sensor cleaning requires opening the furnace and must be done correctly to avoid damage. The issue may also indicate other combustion problems. Expect to pay $80-$200 for professional cleaning or replacement.

High Limit Switch Tripped

The high limit switch detects overheating and shuts off burners to prevent damage. The blower continues to cool the heat exchanger, producing cold air. This happens when a clogged filter restricts airflow, blocked vents prevent air circulation, or the blower motor has problems.

Simply resetting the switch doesn't fix the underlying problem. Repeated overheating can damage the heat exchanger. Professional diagnosis costs $100-$150, plus repair of the root cause.

Gas Supply Problem

Your furnace can't get gas to burn. Check if other gas appliances work and verify the furnace gas valve is in the ON position (handle parallel to pipe). If those check out, the gas valve itself may have failed.

Gas component repairs require expertise because leaks are dangerous. Professional service costs $200-$500 depending on whether it's a valve issue or gas line problem.

Control Board Failure

The furnace control board coordinates the heating sequence. When it malfunctions, the system can't properly activate components. You might see error codes blinking on the board's LED display or experience erratic behavior.

Board replacement requires electrical work and the correct part for your furnace model. Repair costs $250-$600, including the board and labor.

When to Call Dallas Heating and Air Conditioning for Service

Call immediately if you smell gas (evacuate first and call from outside), your carbon monoxide detector alarms, or you see sparks or smoke. For same-day service during cold weather, call (214) 710-2515 if you've tried the DIY checks with no improvement or if your furnace keeps shutting off repeatedly.

Our EPA-certified technicians have served Dallas, Plano, Frisco, McKinney, Allen, Richardson, Carrollton, The Colony, and Lewisville for over 20 years. We understand the unique challenges North Texas furnaces face after sitting idle most of the year.