Car Air Conditioner Blowing Hot Air On One Side

Car Air Conditioner Blowing Hot Air On One Side

Having your car air conditioning blowing different temperatures from different vents is a common and annoying problem. It creates an uncomfortable blended temperature in the vehicle. So why is the car air conditioner blowing hot air on one side?

The most common causes behind an air conditioner blowing hot air on only one side will be a bad actuator, electrical issues, device settings, battery issues, or refrigerant issues. Some of these can be fixed easily whereas others will likely need the services of a mechanic.

I’ll run you through the tests you can perform to narrow down what your exact air conditioning issue is. I’ll also explain some basic steps you can take to fix these issues and also how to work out when you need to go and have expert help.

What Causes The Air Conditioner Blowing Hot Air One Side

Car Air Conditioner Blowing Hot Air On One Side

There are several common causes including a bad blend door actuator, control module, incorrect settings, battery issues, or low refrigerant. Unfortunately, as these systems become more complex, the opportunity for failure increases.

On top of this, your ability to fix these complicated problems is limited by the need for specialty tools and scanning equipment required. However, before going straight to a mechanic and spending money, do some quick tests to work out what the issue is.

Also known as the temperature blend door actuator or vent mode door actuator, this is a mechanism that blocks or allows cool or hot air through. The door or related systems can fail which causes the door to stop actuating.

If you notice a clicking or ticking sound when operating your air conditioning, this could be a sign of a faulty actuator. This is especially the case if you hear the noises when experiencing the symptom of one side only blowing hot or cold air. 

The two most common causes are either a failed mechanical issue or failed sensor. Generally, a gear in the temperature blend door actuator is faulty and the actuator component needs to be replaced. This is possible to be done by someone with little automotive repair experience.

Drivers’ behavior can also be surveyed and monitored. It is clear that a vehicle’s air temperature is changed far more than the mode is changed (defrost, floor heat, dash vents, etc). As the temperature actuators are much more involved in the former, the actuators will generally fail first.

If the actuator fails, it usually fails to leave the opening fully open or fully closed. This means that a good diagnostic test is to operate each temperature control to see which side changes temperature. 

When trying warm settings, the actuator that changes temperature is good, the actuator that doesn’t is bad. This will also help prove the central controller is operating. If the controller is bad, neither actuator would change positions.

Issues with the sensors can cause issues with temperature detection and actuator movement. These can fail over time and report incorrect data.

Other common causes stem from the control module. Problems with the air conditioning control module can be diagnosed with an advanced scan tool available at your mechanic. Given their complicated nature, issues of this type are best handled by an expert.

One of the most common and easiest ways to fix your air conditioner blowing hot on one side only is by checking the settings. Sometimes it blows cold or hot on one side because the internal climate zones have been set this way. This can be remedied by adjusting the temperature on the cold side or vice versa to the preferred degree.

Given that the air conditioning system is electrical, it can suffer from common electrical faults. 

For example, after disconnecting the battery, this may interrupt the control module’s programming. If this happens, the module might collect inaccurate data. This will lead to an inaccurate temperature setting, requiring recalibration.

Low refrigerant is one of the leading causes of drastic temperature differences from one side to the other. Some dual systems have two receptacles of coolant and even slightly variable amounts between the two can result in an ability of the system to maintain an even temperature.

How To Fix Air Conditioner Blowing Hot Air On One Side

Car Air Conditioner Blowing Hot Air On One Side

To replace a faulty actuator, normally you have to remove the glove box. Most models of vehicles will have it in this location. Disconnect any wiring harness and remove the fastening bolts from the actuator. Remove the faulty unit and replace it with a compatible part.

You should target the actuator that is making any weird noises or clicking sounds. It may be possible to fix the actuator if it has obvious debris or issues with it but generally, the best bet is to get a new part.

In regards to low refrigerant, one first step is to top off the system. Another option is to flush the unit and recharge it with the factory-specified amount. This is normally to fix issues relating to the blowing of hot air or if the cooling function seems to be malfunctioning.

A soft reset of the climate system or air conditioning is another good troubleshooting option. Check your manual for your specific model of the vehicle but this generally involves pressing a combination of buttons such as power and heat and holding, but this will vary.

A soft reset should also fix any calibration issues that may have been inadvertently set. This is actually a very common cause of hot air blowing from one vent and cool air blowing from another.

If the program needs to be recalibrated, sometimes it can be reset by disconnecting the battery for about five minutes. After reconnecting the battery, turn the key on and do not touch any air conditioning controls. Turn the key at least to ‘full power’ but do not actually start the ignition.

Gui Hadlich

Hey there! I'm Gui. To be honest, I'm not really that interested in cars. But what I'm really, really not interest in is spending lots of money fixing my car up. Thankfully, I have a father-in-law who's obsessed with cars and a brother getting a PhD in internal combustion engines, so I get to learn about fixing cars. And with Fixing Engines, I hope to help you save a lot of money and take good care of your cars.

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