Are you having trouble with your vehicle’s AC? Does air only blows out of defrost and floor? Well, this is a problem that many car owners have. Over time, some of the vents simply stop blowing air. The reason behind this is a small component of the HVAC system which is easy to replace.
In this blog post, I will be talking about why your vehicle blows air only out of defrost and floor and how to fix it.
What Does a Blend Door Actuator Do?
Blend door actuators control the air and temperature blending and the direction of airflow. The blend door actuators have gears that are rotated by a small motor that moves doors in the HVAC incrementally between 90 and 180 degrees to reach desired air and temperature flow.
The blend door actuator is controlled by the vehicle’s climate controls. Blend door actuator can open and close at various positions to block or allow air to pass through the heater core in order to achieve the desired temperature inside the vehicle.
The mode door actuator controls which vent or vents air blows through. The door on the actuator has two positions: closed and open. The recirculation door actuator allows air inside of the passenger cabin to be recirculated through the A/C system, cooled or heated, and recirculated back into the cabin rather than ambient air.
Fixed: Air Only Blows Out Of Defrost And Floor (With Pictures)
If air blows out of defrost and floor in your vehicle, there is probably something wrong with the blend door actuator. Here is a very detailed guide on how to test the blend door actuator and fix a vehicle that has air blowing out of defrost and floor only:
1. Required materials for the job
- New blend door actuator
- Cabin air filter
- 5.5-millimeter socket
- Safety gloves and goggles
2. Diagnose a bad blend door actuator
Before you replace a bad blend door actuator, you will need to diagnose it and make sure it is bad. Each time you try to select the temperature inside the cabin, or to select which vent to blow air, the computer sends a signal to the blend door actuator. The blend door actuator then redirects the airflow to the selected vent with the correct temperature.
So, each time you choose the temperature or the vent, the blend door actuator engages. A bad blend door actuator will actually only allow air to blow out of certain vents. The temperature may also be incorrect. Also, the best way to actually diagnose a bad blend door actuator is to listen to it. Each time you start your vehicle and turn on the AC, you can hear a squeaking/whining, popping, or clunking noise coming from the dashboard.
3. Order a new blend door actuator
Once you have established that your blend door actuator is bad, it is time to replace it. So, a brand new actuator costs around $30, depending on your make and model. You can either order a new blend door actuator on amazon.com or at your local auto part store. Either way, just make sure that the new blend door actuator is actually compatible with your vehicle.
4. Locate the blend door actuator
The blend door actuator is usually located on the driver’s side, underneath the steering wheel. It might be located in a different spot, depending on your vehicle. So, it is probably best if you check the owner’s manual to see where the blend door actuator is located on your vehicle.
However, as I said, it is probably underneath the steering wheel. It is a little bit hard to reach, so you might need to remove the plastic panel right above the gas pedal and underneath the steering wheel. The key here is to gain as much access as possible in order to remove it.
5. Disconnect the wiring harness connector from the blend door actuator and test it
Before removing the blend door actuator, it is best if you remove the wiring harness connector and test if the current is running through it and powering the blend door actuator. Sometimes the electrical wiring fails and isn’t sending enough power into the blend door actuator.
Turn on your multimeter and set it to 20 DCV. On the bottom left side, there is a green/black port which is always going to be negative, and right next to it there is a yellow/black port which is positive. Turn the key into an on position and first test the negative connection and then the positive connection. The voltage rating should be between eight and twelve volts on both connections.
6. Remove the faulty blend door actuator
After you successfully diagnose that the wiring is alright, it is time to remove the faulty blend door actuator. The blend door actuator is usually secured in place by 3 bolts size 5.5-millimeters. So, grab a 5.5-millimeter socket and remove the bolts. After you remove the bolts, you will be able to pull out the blend door actuator.
7. Install the new blend door actuator
Install the new blend door actuator and secure it in place with the three bolts that you removed from the faulty actuator. Then, reconnect the wiring. Make sure that you connect it all the way. After the blend door actuator is secured and connected, reinstall any plastic covers that you had to remove in order to gain access.
9. Install the new cabin air filter
A high-quality cabin air filter removes dust, pollen, soot, exhaust fumes, unpleasant odors, and even fine particulate dust from the interior air in the vehicle. It also improves air circulation and prevents dangerous fogging of the windows.
However, the cabin air filter performs another important function. In addition to improving the quality of the air entering the vehicle, the cabin air filter reduces the load on the blower and protects the HVAC system from contamination by keeping dirt, debris, bugs, and leaves out of the evaporator and the heater core.
When the filter element becomes clogged, it restricts the airflow through the heater in the air conditioner. When the air intake is restricted, it’s going to decreases the volume of warm air that the heater can blow into the cabin. In the summer, it can have the same effect on the air conditioner. That’s not a good situation for the HVAC system because it forces the heater and air conditioner to work harder depending on whether you want warm or cool air.
Basically, a dirty cabin air filter can restrict airflow to certain vents. Many car owners change their cabin air filters twice a year. However, depending on where you live, you might need to change the cabin air filter more often. It is always a good idea to change the cabin air filter when you replace the blend door actuator just to be safe.
9. Test the AC
At this point, you should be able to change the vents and the temperature of the AC. Before, if your AC blew only on defrost, or on the floor, now, it should blow on all vents, including the dashboard vents. So, start your vehicle and change the AC settings, temperature, and vents.
Why Does My Air Only Work On Defrost?
The AC in your vehicle only works on defrost because the blend door actuator has failed and got stuck into a position where it only allows air to flow on defrost vents. When you turn on the AC and set the desired vent and temperature, the blend door actuator engages and opens and closes vents accordingly. However, when a blend door actuator fails and locks up, air will not come out of some vents simply because the gears inside the blend door actuator got broken and will not open and close the vents.
The blend door actuators are designed to last the lifetime of the vehicle. However, most of them break after 70,000 to a 100,000 miles.
The blend door actuator has a board, connector, a motor that drives it, a drive gear, transfer gear, and an output shaft. The problem with all blend door actuators comes from the drive gear and transfer gear. They are made so small with little plastic teeth on them and they need to be moving a big door inside the HVAC case. That tough role, combined with key cycles makes them fail. Basically, if you open up a blend door actuator, the only thing that will be broken is the drive and transfer gear.