Is Your HVAC Blowing Cold Air in Winter? Here’s What Could Be Wrong

When temperatures drop in Arizona’s winter season, residents depend on their heating systems to keep their homes warm and comfortable. But what happens when your HVAC is blowing cold air in winter? Mountainside Air helps our customers handle this frustrating problem that threatens to leave you and your family facing cold days and evenings. 

There are several possible reasons why your HVAC system isn’t producing heat. Some issues have simple fixes, while others require professional HVAC service. As the leader in expert HVAC services in Avondale, AZ, we want to share the following reasons and remedies for heating system malfunctions. 

1. Check Your Thermostat Settings

Start with the basics. One of the leading reasons that an HVAC system fails to heat properly comes from incorrect thermostat settings or performance. Try these troubleshooting tips first:

• Make sure your thermostat is set to “HEAT” instead of “COOL” or “FAN.”
• If the fan setting is on “ON” rather than “AUTO,” it may continuously blow air, even when the furnace isn’t actively heating.
• If you have a digital thermostat, check and replace the batteries as needed.

2. Inspect and Replace Dirty Air Filters

Dirty air filters can cause significant heating problems when clogged with dust, dirt, and debris. That restricts essential airflow and places unnecessary stress on the entire system.  

If the heating system overheats due to a dirty air filter, the high-limit safety switch may shut down the burners while the blower continues to run. That causes cool air to continue circulating through your living space.

If your HVAC is blowing cold air in winter, always remember to replace or clean your HVAC filters every 30 to 90 days.

3. Is Your HVAC in Defrost Mode?

If you own a heat pump system, the unit’s defrost mode can cause it to blow cold air temporarily.

Heat pumps absorb heat from the outside air to warm your home, and during winter, ice can form on the outdoor unit. The system can automatically switch to defrost mode long enough to melt the ice by temporarily reversing operation.

If your system stays in defrost mode for too long, it could indicate a faulty defrost control board or sensor, requiring professional attention.

4. Check the Outdoor Unit for Obstructions

Blocked outdoor units are often unable to pull in the warm air needed for heating.

Inspect the area around your outdoor unit for:

• Dirt, leaves, or debris accumulation
• Ice or frost buildup
• Physical obstructions like fences or overgrown bushes

Regularly clear debris from at least two feet around your outdoor HVAC unit between regular professional maintenance service calls. 

5. A Gas Furnace May Have Ignition or Pilot Light Issues

If you have a gas furnace, a malfunctioning pilot light or electronic ignition could prevent your system from burning fuel needed for heating. An HVAC technician can inspect modern electronic ignition systems for repairs or precision cleaning. 

If your pilot light goes out, follow the manufacturer’s instructions to relight it safely. However, if it continues to go out or fails to ignite, it’s best to call a professional HVAC technician.

6. An Overheated Furnace Might Be Shutting Down

When an HVAC is blowing cold air in winter, it could be overheated. Safety mechanisms incorporated in HVAC systems can lead to cool circulation, as the blower fan may continue to run even after combustion shuts down.  

The most common causes of furnace overheating include:

• Dirty air filters that restrict airflow
• Blocked vents or registers that prevent circulation
• Mechanical issues like failing blower motors or dirty heat exchangers

7. Other Possible HVAC Issues

If none of the above solutions fix your heating problem, you may be dealing with one of these issues:

• Low heat pump refrigerant levels. Heat pumps require adequate refrigerant levels for both heating and cooling. 
• Faulty reversing valve. Also, in heat pump systems, a malfunctioning valve can flip from heating to cooling mode. 
• Electrical or control board issues. An HVAC professional can inspect for control board or other electrical problems.