Why Is Your Furnace Blowing Cold Air in Jurupa Valley, CA?

Inland Empire Comfort
January 27, 2025
Furnace Repair in Jurupa Valley

If your furnace is blowing cold air, your house will get pretty uncomfortable fast. Many Jurupa Valley residents run into this problem, particularly when they first turn on their heat after not using it for a while.  


At Inland Empire Comfort, we provide furnace repair in Jurupa Valley and understand the ins and outs of why a furnace blows cold air. We'll determine exactly what's wrong and get your heat working again. 


Keep reading to learn what might be going wrong with your system and how to get your home cozy again. 

Possible Reasons Your Furnace Is Blowing Cold Air 

When you turn on your gas furnace, it doesn't blow hot air right away. First, the burners light up. The fan waits a bit before starting and will need to push out all the cold air sitting in your ducts. 

Don't worry if you feel cold air coming out at first—that's just how furnaces work. But if it stays cold after a few minutes, something is probably not right. 


A Faulty Thermostat 

A defective thermostat can blow cold air when thermostat settings are wrong: either stuck on "cool" instead of "heat," running on "fan" instead of "auto," or set too low. Sometimes, broken wiring between the thermostat and the furnace causes constant cold airflow.  

You want to set the temperature above 68°F, like 72°F, to trigger heat. Sometimes, faulty thermostat wiring may prevent communication with the furnace, requiring you to call an HVAC professional to diagnose the issue. 


Dirty Air Filter 

When the filter gets clogged with dust and debris, it blocks the normal flow of air into the furnace. Without enough air flowing through, the furnace can't properly heat what little air makes it past the filter. This triggers safety switches that shut off the burners to prevent damage from overheating. 


As a result, your furnace just pushes around room-temperature air without warming it up. Even though you have the heat on, you'll stay cold because the blocked airflow stops the furnace from doing its job of heating the air. This is a common reason why a furnace blows cold air.


Blocked Airflow 

Small or blocked ducts mean less air flows in, so your furnace struggles to heat what little air it gets. Clogged filters or poorly sized ductwork are common culprits.  


The result is that your furnace gives up and blows cold air instead of keeping your home cozy.


Circuit Control Board Malfunction 

If the control board breaks, the furnace can't run its basic functions properly. The board might still run the blower fan but fail to ignite the burners, resulting in cold air blowing through your vents.  


This typically happens when dirt builds up on the board, or water from a leak damages its electrical components. You need to act quickly to prevent complete heating failure.  


Leaky Ducts 

Leaky ducts are like throwing away money and comfort. When your furnace pushes heated air through damaged ducts, up to 30% of that warmth escapes into unused spaces like crawl spaces and walls. Meanwhile, holes in the ductwork suck in cold air from unheated areas.  

By the time air reaches your rooms, it's a disappointing mix of heated and cold air. This explains why you might feel chilly even with the heat running.  


A Damper Issue 

If your ducts have closed or stuck dampers, warm air can't get to parts of your house. Your furnace cranks up to compensate, working overtime to heat those cold spots. When it works too hard, it overheats and automatically switches to cold air to protect itself from damage.  


This happens pretty often—the furnace basically hits the brakes to prevent further damage. A simple damper adjustment might be all you need to fix the issue.  


Pilot Light or Ignition Issues 

If your furnace's ignition system fails, you'll get cold air because there's no flame to heat it. In modern furnaces, a dirty flame detector can shut off the heat while the blower keeps running.


Older furnaces with pilot lights can have similar issues—if debris blocks the pilot or it burns yellow instead of blue, you won't get proper heating. Either way, no flame means cold air, which is a common reason why a furnace blows cold air. Without proper ignition, the system can't generate heat, leaving you with chilly airflow.


Lack of Fuel (Gas Furnaces) 

When your furnace doesn't get enough gas, it can't create the flame needed for heating. Just like your car needs fuel to run, your furnace needs gas.  


If there's a problem with the gas valve or you're running low on propane, the furnace will still blow air—it just won't be heated. You can spot this issue if your other gas appliances aren't working either.  


Triggered Safety Mode 

When your furnace overheats, its safety switch kicks in to prevent damage. This causes it to blow cold air until things cool down, which explains why you might notice your furnace alternating between hot and cold air output; it’s actually protecting itself.

 

Faulty Main Limit Switch 

A faulty limit switch may incorrectly tell your furnace it's overheating even when it's not. This false alarm triggers the safety shutdown, stopping the heating cycle. Instead of producing warm air as it should, your furnace just blows cold air until a professional replaces the broken switch.  


Heat Exchanger Problems 

A cracked heat exchanger is a dangerous furnace problem that can make your home's air stay cold. When this critical part breaks, it can't properly heat the air flowing through your furnace.  


Worse yet, deadly carbon monoxide gas can leak into your home's air. You need immediate professional help if this happens.  

Schedule Reliable Furnace Repair

Schedule Reliable Furnace Repair  

Is your furnace blowing cold air? Time for annual furnace maintenance? Our technicians at Inland Empire Comfort will determine what's wrong and restore your comfort. We'll explain exactly what needs to be done and get your heat back up and running fast. 


We fix furnaces—both urgent breakdowns and regular upkeep. Big job or small, we'll do the job right. Call Inland Empire Comfort when your furnace needs repair or for more information on why a furnace blows cold air.

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