Heater Blowing Cold Air? Furnace Problems in Hampton and Newport News

A furnace that blows cold air, runs without stopping, shuts off after a few minutes or keeps tripping its breaker often has a cause you can check in five minutes. Other times a safety control has shut the burners down, and that needs a technician. Here is how to tell which one you have.

Why is my furnace blowing cold air?

A furnace blows cold air when the blower is running but the burners are not, and the most common reasons are a thermostat fan set to ON, a clogged air filter, or an ignition problem. With the fan on ON, the blower keeps running between heating cycles and pushes room-temperature air through the vents. A clogged filter starves the furnace of air, the heat exchanger overheats, and a safety switch called the high limit shuts the burners off while the blower keeps running to cool things down. Burners that light and go out within seconds usually point to a dirty flame sensor. High-efficiency furnaces add one more cause: a clogged condensate drain can stop the burners too.

Cool air for the first minute after the furnace starts is normal, because the ducts are cold. Cold air that lasts longer is not. If your home has a heat pump instead of a gas furnace, air that feels lukewarm is often normal, and our winter heat pump guide covers what to look for.

What you notice	Likely cause	What to do
Cool air between heating cycles, fan never stops	Fan set to ON	Set the fan to AUTO
Burners light, then go out within seconds	Dirty flame sensor	Call for service
Heat for a few minutes, then only the fan runs	Clogged filter tripping the high limit	Replace the filter, call if it repeats
Cold air and water around a high-efficiency furnace	Clogged condensate drain	Call for service
Cold air and the gas stove or water heater is out too	Gas supply	Call your gas company

What should I check before calling for furnace repair?

Five quick checks solve a fair share of no-heat calls, and our office walks callers through the same ones before booking a visit:

1. Thermostat. Set it to HEAT, a few degrees above room temperature. Replace the batteries if the display is blank or dim.
2. Fan setting. AUTO, not ON.
3. Air filter. If you cannot see light through it, replace it.
4. Power. Check the furnace breaker in the panel and the service switch on or near the furnace, which looks like a light switch. Reset a tripped breaker once.
5. Vents. Supply vents open and return grilles clear of furniture and rugs.

If the furnace still blows cold after those, the cause is inside the unit: the igniter, flame sensor, a safety switch, the control board or the gas valve. Those are technician jobs, because they involve the gas and safety controls.

Why does my furnace keep running?

On the coldest nights, a furnace that runs almost nonstop is usually keeping up, not failing. When a cold snap drops the Peninsula into the 20s, a furnace sized for our mild winters can run long cycles to hold the setpoint, especially with the thermostat set high. Constant running is a problem in three cases. First, the house never reaches the setpoint even in mild weather, which usually means a dirty filter, leaky ductwork or a furnace too small for the house. Second, the blower runs nonstop with the fan on AUTO, which can point to a failed limit switch, relay or control board. Third, warm air keeps coming after the thermostat is satisfied, which is also a control fault. For either control fault, you can shut the furnace off at the thermostat until we get there.

Why does my furnace turn on and off so often?

A furnace that lights, runs a few minutes, shuts off and starts again is short cycling, and the most common cause is overheating from restricted airflow. The high limit switch shuts the burners off when the heat exchanger gets too hot, the furnace cools, and the cycle repeats. Start with the filter and any closed vents. Other causes are a dirty flame sensor, a thermostat mounted near a supply register or in direct sun, a blocked flue or vent pipe, and a furnace too big for the house. An oversized furnace heats the air near the thermostat quickly and shuts off before the far rooms warm up. No repair fixes that one; it gets solved with a load calculation at furnace replacement time.

Short cycling is worth a service call because of what it can hide. Last November a Hampton homeowner called us about a furnace that ran about 15 minutes, then kept cycling and flashing a high-limit code. Our technician’s flame test showed the heat exchanger pulling the flame inward, a sign of a crack, and we recommended replacement. A cracked heat exchanger can leak combustion gases, including carbon monoxide, into the home, so it is not something to run through the winter.

Why does my furnace keep tripping the breaker?

A furnace that trips its breaker once may have caught a power flicker, but one that trips again after a reset has an electrical fault, and resetting it over and over can damage the motor or wiring. The usual causes are a blower motor that is wearing out and drawing too much current, a failing motor capacitor, or worn wiring that shorts. A clogged filter or blocked vents make the blower motor work harder and can push a weak motor over the edge. Less often the breaker itself has worn out.

Last February a caller told us he had reset his furnace breaker several times overnight. Each time the furnace ran for a while and tripped again. That pattern means the furnace needs a technician. Reset once, and if it trips again, leave it off and call us. If you smell burning or see smoke, shut the furnace off at the breaker and leave it off until a technician arrives.

Frequently Asked Questions

When is a furnace problem an emergency?

Leave the house right away if you smell gas (a rotten-egg odor) or your carbon monoxide alarm goes off. Once you are well away from the house, call 911 and your gas company. A burning smell or smoke from the furnace also calls for same-day service.

Does Kearney & Sons repair all furnace brands?

Kearney & Sons services all makes and models, including Goodman, Trane, Carrier, Ruud and Daikin furnaces. We install Bryant, York, Rheem and Bosch equipment, and our technicians are NATE certified.

Furnace still blowing cold air?

If your furnace still blows cold air after the basic checks, keeps tripping its breaker or short cycles, Kearney & Sons can help. We repair furnaces across Hampton, Newport News, Williamsburg, Yorktown and the rest of the Peninsula, with 24/7 availability for no-heat emergencies. Schedule furnace repair or request service online. A yearly fall tune-up cleans the flame sensor and checks the safety controls before the first cold snap.

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