Why Is My AC Light Blinking In My Car? (11 Reasons Why)

Almost all modern-day cars come with AC to keep passengers cool throughout their journeys. Many of these AC units will also come with a light on the dashboard.

If you noticed your AC light is blinking in your car, you might be wondering what the cause is. We looked up the facts, and here is what we found!

Why Is My AC Light Blinking In My Car?

An AC light typically blinks in the car because of an issue with the compressor clutch, clutch relay, or belt of the AC unit. Also, the AC unit may need maintenance, such as replacing or cleaning the air filters. Plus, the AC unit’s filters or the unit itself may be improperly installed.

Are you curious to learn more about what makes your car’s AC light blink? We made a list of factors below, so keep reading!

1. Compressor Clutch

Generally, your compressor clutch is considered the core of your car’s AC system since the compressor clutch helps turn on the AC.

Typically, the compressor clutch communicates with the AC compressor when turning on and off.

When your AC turns on, the pulley in the compressor clutch turns the compressor clutch hub.

However, if the clutch slips, your AC light will continuously blink whether the AC is turned on or off.

2. Old AC Belt

An AC belt attaches the engine crankshaft to the AC compressor clutch to let the compressor turn on using the engine’s power once the AC gets turned on.

However, an AC belt can get worn out over time, so an old AC belt can make the clutch slip and cause malfunctions in the compressor.

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Normally, you would know if the AC belt is the issue if you hear a squealing noise whenever you turn the AC on.

3. AC Pressure Switch

Your AC pressure switch is a kind of switch that watches the refrigerant’s pressure on both sides of your AC system.

Further, this pressure switch features two pressure thresholds: a low-pressure switch and a high-pressure switch.

Whenever one of these switches decides to trip, your HVAC unit will make your AC light blink, which can lead to your AC shutting down.

Normally, this issue can be resolved by resetting the switches or restarting the thermostat subbase system and the main panel circuit breaker of the HVAC unit.

4. AC Clutch Relay

Your AC clutch relay is in charge of giving power to your AC clutch and compressor, but a failing AC clutch relay could be causing your AC light to blink.

If there is no relay, there will be no power for your AC compressor, and your AC can malfunction, causing the AC light to blink.

Therefore, if you want to find out if the cause of your blinking AC light is the clutch relay, you can swap your horn relay with your clutch relay.

5. Lack Of Belt Tension

As mentioned earlier, an old AC belt can make your AC light blink, but you should also check the belt tension.

Generally, the drive belt tensioner is a pulley mounted on an adjustable pivot joint or spring mechanism to ensure the engine belts have tension.

If the belt tensioner is weak, the clutch can slip, thus affecting the functionality and performance of your compressor clutch, leading to a blinking AC light.

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6. Low Refrigerant Levels

Low Refrigerant Levels

Refrigerant is a fluid that your car’s AC system needs, and most cars require a specific level of refrigerant to ensure the AC functions properly.

So, whenever your refrigerant levels are too low, the AC unit will sense it and make your AC light start to blink.

Generally, you can check how much refrigerant you have since the AC unit has a meter to measure how much refrigerant should be in the car.

7. Electrical Issues

Another common cause of an AC light blinking in your car is an electrical issue in your AC unit.

Usually, this would be because there is irregular power loading or drawing, causing the electrical wiring or circuit board to malfunction.

Normally, this can be fixed by resetting the power switch of the AC unit, especially if a power surge causes the blinking.

8. The Filter

Almost all AC units have filters that clean air that circulates through the unit, but the filters will eventually get clogged with dirt.

If the AC filter is dirty, the AC will struggle to release air from the AC unit, causing various issues like a blinking AC light.

Also, an incorrectly installed filter can cause make your AC light to blink, but this will be resolved once you install the filter properly.

9. Poor Air Circulation

Occasionally, if your car’s AC unit struggles to circulate air through its system, the AC light will blink.

That said, there are a number of reasons why your AC unit is experiencing poor circulation, and you can usually check for error codes to see the cause.

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Also, this could be caused by an improperly installed or clogged air filter, as mentioned earlier.

10. Improperly Installed AC Unit

Sometimes, a poorly installed AC unit can cause several issues, including a blinking AC light.

This is often the case if there are no actual problems with the AC unit, meaning the AC unit just has to be reinstalled to avoid errors like a blinking AC light.

11. Maintenance

Generally, all AC units require check-ups to ensure they are running efficiently since they can eventually have issues like a blinking AC light.

Normally, you would need to have your car’s AC unit checked once at least every six to 12 months.

To know more, you can also read our posts on why your car AC control panel is not working, why your car defrost is not working, and why your car smells like rotten eggs.


Generally, a blinking AC light in your car can signal various problems, the most common being a problem with the compressor clutch, AC belt, and clutch relay.

Additionally, other issues such as maintenance issues, an improperly installed AC unit, or filter can cause your AC light to blink.

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