AC Blows Cold on One Side and Hot on the Other?

AC Blowing Cold on One Side and Hot on the Other

Diagnose and Fix

If the car AC blows cold air on one side and hot on the other, there are a few different causes but it’s likely the blend door actuator, also known as the temperature blend door actuator or vent mode door actuator. We’ll cover what can cause your car’s AC to only blow hot or cold on one side, what other symptoms you might hear, and how to diagnose the blend door actuator if you think it’s the cause.

Fix your blend door actuator yourself with quality auto parts at 1aauto.com

Signs of a Temperature Problem in Your Car

AC Blows Cold Air One Side and Hot Air on the Other

There are a few different reasons why the AC might not work in your car. If the air conditioning in your car is blowing hot air on one side and cold air on the other, there could be a simple fix like adjusting the temperature or it could be time to replace a part like the temperature blend door actuator.

AC Blows Hot or Cold Air on One Side with Clicking Sound

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, it probably means a gear in the temperature blend door actuator is faulty and the actuator needs to be replaced.

Why the AC Blows Cold on One Side and Hot on the Other

Problems with the HVAC control module can be further diagnosed with an advanced scan tool, but here are some common reasons why the AC might be blowing hot and cold air on either side despite the set temperature settings.

Temperature Settings Adjusted Differently for the Passenger and Driver Side

HVAC controls - Testing If the AC blows cold on one side but hot on the other.

Sometimes the AC blows cold on one side and hot on the other because the settings are set that way. This can be remedied by adjusting the temp on the cold side or vice versa to the preferred degree.

HVAC (Heating, Ventilation, and Air Conditioning) Control Module Program Needs a Reset

After disconnecting the battery, sometimes you can interrupt the HVAC (heating, ventilation, and air conditioning) control module’s program that conducts a self-test to find the blend door actuator’s location. If this happens, the module might read inaccurate data, leading to an inaccurate temp and requiring recalibration.

If the program needs to be recalibrated, sometimes it can be reset by disconnecting the negative terminal on the battery for about 5 minutes. After this, turn the key on and do not touch any HVAC controls. Hopefully this will reset the module.

Faulty Blend Door Actuator

A Bad Blend Door Actuator - The Common Cause of Car ACs Blowing Cold on One Side and Hot on the Other.

The blend door actuator, also known as the temperature blend door actuator or vent mode door actuator, can break or malfunction over time. A blend door actuator is faulty if the HVAC control module commands it to a certain position but it fails to comply, leading to situations like the temp blowing hotter or colder than its intended setting. A faulty blend door actuator can be identified with a powerful scan tool and sometimes makes a clicking noise from worn or broken internal parts.

Mechanical Problem with Vent Door

Sometimes the temp will blow hotter or colder on one side from mechanical problems with the vent door. Sometimes the door can jamb or stick, or have issues being controlled.

Temperature Sensor Not Working

If the temp sensor isn’t working and the vehicle has a hard time picking up accurate information, this can affect the way the temperature settings work.

Head Unit or HVAC Controls Not Working

Sometimes the head unit or heat and A/C controls cause the A/C to blow hot or cold air on one side. Commands may work intermittently or not at all, making it difficult to control the temperature settings.

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How to Diagnose Blend Door Actuators

Diagnosing a temperature blend door actuator with a scan tool

Blend door actuators are the most common reason for the car air conditioning to blow cold air on one side and hot air on the other. They can be diagnosed with an advanced scan tool. The scan tool can tell if the blend door actuator should be in a different position than commanded. If it does not move with the adjustments and commands, there is a problem with the blend door actuator and it will need to be replaced. If the actuator is clicking, this is another sign it will probably need to be replaced.

Where Is the Blend Door Actuator Located?

Temperature blend door actuator location
Temperature blend door actuator located on the driver side, above the accelerator pedal and on the side of the HVAC box

The actuator is usually screwed in with an electrical connector on the corresponding driver or passenger side. Sometimes they are placed above or below the heater box, also known as the HVAC box.

How to Replace the Blend Door Actuator Yourself

Replacing the door lock actuator can be an easy repair. These are the steps to replace a blend door actuator on a 00-03 Chevy Monte Carlo

  1. Remove the Glove Box
  2. Remove the Temperature Door Actuator
    1. Disconnect the temperature door actuator wiring harness
    2. Remove the two 7/32 inch bolts from the actuator
    3. Pull off the actuator
  3. Install the Temperature Door Actuator
    1. Line up the shaft with the new actuator
    2. Push the actuator into place
    3. Insert the two 7/32 inch bolts into the actuator
    4. Connect the actuator wiring harness
    5. Test the actuator by moving the temperature control and watching the actuator
  4. Install the Glove Box

Check out this video to see the replacement on an 08-12 Ford Escape. To find videos specific to your year, make, and model, search 1A Auto’s how-to videos.

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Car AC Blows Cold on One Side and Hot on the Other - Diagnose and Fix
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Car AC Blows Cold on One Side and Hot on the Other - Diagnose and Fix
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If the car AC blows cold air on one side and hot on the other, there are a few different causes but it's likely the blend door actuator, also known as the temperature blend door actuator or vent mode door actuator
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