Why are half of my vents blowing cold air?

Author: Dr. Mitchel Strosin  |  Last update: Monday, September 22, 2025

If you're experiencing hot air on the driver side vent and cold air on the passenger side vent this can be caused by a stuck blend door or failed blend door actuator motor. Clicking noise from the dashboard is usually caused by a failing blend door actuator. In addition, low freon/refrigerant can also cause this issue.

Why are some of my vents blowing cold air?

The heat exchanger uses coils to transfer heat from the ignited gas to the air. When cold air blows from a furnace the heat exchanger, furnace burner, or exhaust are likely the cause. This may be due to dirty components, broken parts, or the many safety mechanisms within the gas system.

Why is my car blowing heat on one side and cold air on the other side?

Low refrigerant is the main reason for the extreme temperature difference between one side of the dash and the other due to the design of dual AC systems. Even experienced auto mechanics might be shocked to hear about such a significant difference.

Why is half my heater blowing cold air?

If your heater is blowing cold air, this suggests that there is a problem with the heater core. This problem could be that the core is clogged or leaking.

Why is my AC only cold from one vent?

If you experience the symptom of the AC blowing hot or cold air on one side but not the other and it's accompanied by a clicking or ticking sound from the dashboard, it probably means a gear in the temperature blend door actuator is faulty and the actuator needs to be replaced.

Furnace blowing COLD air out vents - 3 MOST common causes!

Why is only half of my AC cold?

Dirty Air Filters

Eventually, the system won't be able to circulate air effectively, causing uneven cooling and warm spots where the colder air cannot reach. Dirty air filters can significantly reduce your air conditioner's efficiency and contribute to more mechanical breakdowns.

How do you fix an uneven airflow in HVAC?

Dealing with Uneven Air Flow
  1. Make sure your vents are uncovered/unblocked. ...
  2. Make sure your vents are fully open. ...
  3. Make sure you clean/replace HVAC filters. ...
  4. Make sure your windows are adequate. ...
  5. Duct leakage. ...
  6. Inadequate duct size. ...
  7. Damaged or improperly installed ducts. ...
  8. Improper return vents.

Why is only half my house cooling?

Your air conditioning system may produce uneven cooling in your home due to various faults. Issues with air ducts, HVAC equipment, and more can cause a central air system to fail at cooling a home evenly. Vents Are Blocked: Room vents distribute cold air from supply ducts.

What are the symptoms of a clogged heater core?

Signs Your Heater Core is Not Working
  • The Heater Just Plain Doesn't Work.
  • The Windshield Won't Defrost.
  • Is That Antifreeze I Smell?
  • Coolant Leaking into the Cabin.
  • The Engine is Running Hot.

Why is one room blowing cold air?

Inadequate Insulation: Poor insulation in a specific room can result in heat loss, making it colder than the rest of the house. Check the insulation in the walls and ceiling of the affected room. Adding extra insulation or caulking gaps around windows and doors can help improve insulation.

How to tell if freon is low in AC car?

One of the most obvious signs that your vehicle needs a Freon recharge is that your vehicle will be blowing warm air, even after your vehicle has been running for some time. If your refrigerant gets too low, there will simply not be enough “coolant” to cool the air as it is passed through your evaporator coil.

Why is my AC blowing cold air on one side?

If you're experiencing hot air on the driver side vent and cold air on the passenger side vent this can be caused by a stuck blend door or failed blend door actuator motor. Clicking noise from the dashboard is usually caused by a failing blend door actuator. In addition, low freon/refrigerant can also cause this issue.

Why is my car blowing hot air on one side and cold air on the other?

Malfunction of a temperature door.

Vehicles that have drivers and passenger climate controls have two sets of electric motors and doors. If one of the doors is not working it is possible that it could cause heat to come out of one side and a/c to come out of the other.

How do I reset my AC vents?

In AC systems, the air conditioner reset button is on the outside unit's lower edge, typically close to the ground. Some models have the reset button located behind the service panel, which may require tools to remove. Reset buttons are usually red or yellow with a clear “reset” label.

How do I know if my AC vents are clogged?

You can generally identify a blocked air duct by a distinct drop in heating and cooling efficiency, increased energy costs, and occasionally a musty, dusty smell throughout the home. The blockage usually comes over time, by a buildup of dust and debris that just accumulates until it begins choking the system.

How do you unclog a heater core in a car?

Now, here's how to perform a heater core flush:
  1. Step 1: Locate the Heater Core. ...
  2. Step 2: Disconnect the Heater Hoses. ...
  3. Step 3: Apply the Pressure. ...
  4. Step 4: Hit it with the Hose. ...
  5. Step 5: Reconnect the Heater Hoses. ...
  6. Step 5a: Flush your entire cooling system with Thoro-Flush. ...
  7. Step 6: Refill the Coolant.

How to tell if heater core or thermostat is bad?

Five Signs Of A Car With A Bad Heater Core
  1. 1) Your Car Has Odd Smells. Your car's odd smells could indicate a bad heater core. ...
  2. 2) Your Car Is Foggy Or Steamy. ...
  3. 3) You Are Losing Coolant Constantly. ...
  4. 5) Your Passenger Compartment Is Cold.

How much does it cost to unclog a heater core?

You will need tools like 50/50 pre-mixed coolant, an air compressor, and a cooling system vacuum fill tool. A heater core back-flush requires you to prepare the vehicle, perform the back-flushing process, and refill the cooling system. Prepare to pay between $100 and $250 for a professional heater core flush.

Why is half of my house warm and the other cold?

Inadequate insulation can drastically affect your home's temperature balance. Improperly installed or deteriorating insulation in your walls, attic, roof, or ceiling can create drafty areas that can't be adequately heated or cooled. Improperly insulated doors and windows can also cause uneven temperatures.

Why is my AC not working in half of my house?

Check the Vents

When one room in your house isn't cooling, the first thing to check is the AC registers, or vents, in that particular room. The simplest reason that you have uneven home cooling is just that there's something blocking the vent or that you have one or more closed vents.

How do you fix an uneven airflow in your house?

5 Ways to Solve Uneven Home Cooling
  1. Use Your Air Vents to Control and Redirect Air. Look around to see if you have any blocked or dirty vents. ...
  2. Switch the Fan from "Auto" to "On" Look at your thermostat. ...
  3. Have Your Air Ducts Checked for Air Leaks. ...
  4. Add More Insulation in the Attic. ...
  5. Control Different Areas with a Zoning System.

Why is my AC only cooling half the house?

BLOCKED VENTS

If they're blocked with dirt or debris that accumulates over time, the cool airflow will be reduced, keeping the room warmer than others in your home. Your vents should be cleaned regularly and can even be cleaned by you without hiring a professional.

Why are some of my vents not blowing air?

Obstructed Vent

Furniture, bedding, and the vent damper could all be possible obstacles to the vent. If you find any closed or blocked vents, you can clear away the obstruction and feel for airflow, but if your vents are open and still not blowing enough air, there could be an issue with the fan's motor.

How much does it cost to balance air ducts?

How much does it cost to have your HVAC system balanced? Getting an air balance in HVAC systems, with no significant issues or modifications, can range from about $200 to $500. This typically includes airflow measurements, adjusting dampers, and ensuring proper temperature distribution.

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