Hey, Why Does My Car's AC Sometimes Work And Sometimes Don't?
Is Your Car's AC Inconsistently Working?
It’s only working sometimes because the cabin air filter is too dirty, the “mode” door motor is faulty, or the variable compressor is stuck. Alternatively, the following parts might intermittently malfunction: the ac control unit, the ac high-pressure switch, and the evaporator temperature sensor.
Are you experiencing an unpredictable AC system in your car? One moment, it's working fine, and the next, it's not cooling at all?
Don't take this issue lightly! Ignoring it could put your safety at risk and lead to costly repairs. Instead, consider discussing with a professional to address the problem immediately.
Doing so ensures your vehicle remains in good working order, and you can drive it carefree, knowing your AC system functions consistently. Don't let a minor AC issue become a significant problem that could have been avoided with timely maintenance.
Let's Get To The Bottom Of It!
The cabin air filter is responsible for cleaning the air that flows through the air conditioning system in your car. Unfortunately, this filter accumulates dirt, mold, and debris as time passes, building a blockage that restricts airflow. This blockage can cause your air conditioning system to cool less than usual and decreases the air from the vents. Therefore, regularly replacing your cabin air filter is essential to ensure that your AC system functions optimally and provides clean and cool air.
Modern cars use computer-controlled air conditioning systems with a particular type of compressor called a variable vane compressor. This compressor is designed to reduce the electrical load on the engine. A swash plate inside the compressor adjusts itself to change the pressure needed to control the climate inside the vehicle. This means the compressor works efficiently, regardless of the outside temperature. However, since the system is computer-controlled, it can experience failures. If it fails, the check engine light activates, signaling an issue that needs attention.
Your car's air conditioning system has several doors in its box that merges hot and cold air and direct it to where it must go. The Mode door motor is usually connected to a lever mechanism that controls multiple doors. However, if the Mode door motor gets miscalibrated, it causes air to come out of the wrong vent or not come out at all. This happens due to an intermittent connection that causes the motor to function only sometimes or stall, directing air to the wrong location.
The AC control unit in your car is often built into the same panel as the fan and temperature knobs. Over time, the switch on this panel can wear out. When a switch wears out, it sends the wrong or no signal. This can cause problems for switch-controlled components, like the blower and air door control motors. For example, if one of the temperature switches is malfunctioning, it sends the wrong signal to the blend door on one side, causing the temperature on that side to be different.
The AC high-pressure switch is essential to keep your car's air conditioning system running smoothly. It's responsible for monitoring the pressure on the "high" side of the system. If the high side pressure is out of range, the pressure switch signals to the climate control module about a problem with the AC system. If this happens, the compressor shuts off, meaning no cooling comes from the climate control system. Sometimes, however, the pressure switch can be erratic. This means it may shut the AC system off even if the pressure is within the normal range.
The evaporative temperature sensor is a small but essential part of your car's air conditioning system. It's located in the airbox before the evaporator core, and it determines the core's temperature. This information is crucial for maintaining your AC system's efficiency. Another essential function of the temperature sensor is to alert the climate control module if the evaporator freezes over. If the sensor registers a temperature colder than the actual temperature of the evaporator, the climate control module thinks that the evaporator is frozen. This causes the AC system to shut down until the temperature rises.
Find Professional Help
Vehicle Health Inspection Proof
Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.
- Dirty cabin air filter
- Stuck variable compressor
- Faulty mode door motor
- Intermittent ac control unit
- Intermittent ac high-pressure switch
- Intermittent evaporator temperature sensor
The proof image shows the restricted cabin air filter, highlighting the importance of regular maintenance and replacement of filters to ensure the efficient operation of the air conditioning system.
A customer brought their vehicle to the shop and mentioned the air conditioning was not cooling as usual. They thought the blower motor was wearing out because the air from the vents did not feel as sturdy.
During the test drive, the technician noticed the air conditioning was not cooling as expected, and the air from the vents was weak. So the technician conducted a vehicle health inspection to determine the cause of the issue. After checking the components, they found that the cabin air filter was clogged, reducing airflow.
The cabin air filter purifies the air before it goes through the evaporator core. However, over time, the filter clogs with dirt, mold, and debris, restricting the airflow and reducing the cooling performance.
The technician recommended replacing the cabin air filter to restore the airflow to normal. After replacing the filter, the technician checked the air conditioning system's performance. First, they used an AC machine to check the pressures in the air conditioning system and found that they were running in the normal range.
They also checked the temperature coming out of the center to vent with the AC on high and found that the vent temperature was at 38°, indicating that the AC was performing efficiently.
1/6Typical Fixes to Address the Cause(s)
The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.
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Vehicle Symptoms
Below are just a few examples of typical Symptoms and Fixes your car might be experiencing
Other things your auto repair shop might talk about:
Car AC sometimes works sometimes it doesn't. Car air conditioning. Electric blower motor. Air compressor. Air blowing.