Why Isn't Your Car's Automatic Climate Control Working?


March 11, 2020

There was a time when automatic climate control was a novelty reserved for only the most expensive and luxurious vehicles. As automotive technology has advanced, features like automatic climate control have made their way into more and more mass-market models. While this technology can help keep you cool and comfortable, it also comes with its fair share of problems.


If your car's automatic climate control problem is acting up, then the problem may lie with any of the components only tangentially related to your car's actual heating and cooling systems. The complexity of these systems means there are many potential failure points. These three possible problems will help to point you in the right direction.


1. Faulty Control Module


The terminology for this component can vary based on your car's make and model, but the control module is the physical unit located inside the cabin. This component contains the buttons, dials, and screens that you use to adjust the cabin temperature. In most cases, it also includes the electronic hardware necessary to control your heating and cooling equipment.


A faulty control module can produce a vast array of different symptoms. Since you're poking and prodding at the controls regularly, mechanical issues are not uncommon. These can take the form of damaged screens, broken buttons, loose dials, and any number of other defects. Unfortunately, replacement of the whole module is often the only solution.


Electronics failures within the module may have more unpredictable results. In some cases, your climate control may stop responding to your temperature settings or otherwise behave erratically. Odd, seemingly random behavior of the system typically points to an electronic issue.


2. One or More Failed Sensors


If your control module is working correctly, then a failed sensor may be to blame. The most straightforward climate control systems still require two sensors: an ambient temperature sensor located outside of the car and an interior cabin temperature sensor. Together, these two sensors determine the strength and temperature of the air coming from your vents.


More sophisticated systems on higher-end vehicles may also use additional sensors. Most modern cars have multiple temperature sensors located within the cabin to help provide more even heating and cooling. Your car might even have sensors to compensate for the strength of sunlight entering through your windows or to check the body temperature of vehicle occupants.


With so many sensors, a faulty reading from one or more can drastically impact the efficiency of your vehicle's heating and cooling systems. Fortunately, bad sensors will often trigger a fault code in the car's computer.


3. Bad Blend Motors


The complexity of an automatic climate control system doesn't end with control modules and sensors. Most systems use specialized motors to control the exact temperature of the air entering the cabin. These electric motors allow the climate control system to blend the amount of warm or cold air entering the cabin to maintain your desired temperature.


A broken blend motor may stop functioning entirely, or it may no longer be able to report its position to the control module. Since the control system must be aware of the motor's position to control air temperature properly, either situation can lead to unusual behavior. A failing motor may also produce noticeable noises, even if it is not yet impacting the system's operation.


Unless the problem with your climate control system is as simple as a blown fuse, you likely won't be able to diagnose it yourself. As vehicle HVAC systems become more and more complex, proper diagnosis and repair move beyond the ability of shade tree mechanics.


If your automatic climate control system doesn't seem to be functioning correctly, then Letcher Bros. Auto Repair is here to help. Give us a call, and we'll help you to restore your car's heating or air conditioning system to like-new condition.

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