Can AC Compressor Drain Battery? (Explained & Helpful Tips)

A car’s air conditioning is one of the most useful yet complicated systems. The AC ensures you have the perfect temperature inside your car as you drive.

Similar to other parts in your vehicle, the parts in your AC are prone to fail from time to time. To resolve AC issues, you must find the source of the problem so that you can know what to replace or fix.

Today, we are going to look at AC compressor issues and whether a stuck AC compressor clutch can drain your battery.

Here is the thing, if the AC clutch relay is stuck closed, it forces your AC to stay on and this drains your battery fast.

The rule of thumb is to always use the AC when the engine is running. So, should the AC accidentally turn on when the car is off, your battery will be dead in a couple of hours.

Even though a faulty AC compressor can drain your battery, it is essential that you rule out other things that may also lead to a similar result.

If you leave your headlights on, all night long, your battery will be dead by morning. We will look into some of these causes later on, for now, let’s stick to the AC compressor clutch.

can ac compressor drain battery

The most obvious sign that your AC compressor is misbehaving is when you can feel cold air coming from the vents yet the AC is turned on.

That is a clear indication that the clutch is stuck and it’s not coordinating with the controls on your console. Also, when you pop the hood of your car, you should notice some freezing on one of your AC hoses.

And if you can pull one of the relays that powers the AC and shut it off, if the AC compressor relay is stuck, your battery shouldn’t be drained once you boost it.

If your AC compressor relay is stuck, the only solution is to replace it. Once you pull it out, look for an exact replacement and install it.

This should enable the AC compressor to switch as per the instructions you have given on the center console. If you switch the AC off, the AC should do just that.

For those who might have troubles with replacing the AC compressor clutch, now that you know where the problem is, you can hire a mechanic to help you out. The mechanic can also help diagnose other problems that are causing your battery to die.

What is an AC Compressor?

We don’t need to go too much into the work of AC in your car as this is something you already know.

However, you need to know about the AC compressor which is an important part of your AC system. Without an AC compressor, the AC can’t work and even if it does, it will be malfunctioning.

The AC compressor puts pressure on the refrigerant so that your AC system can activate the heat-transfer features. It is the same compressor that ensures you enjoy cool weather in summer and when it gets cold, your windshield is always clear.

Inside the AC compressor, you will find the pulley which has an electromagnetic clutch. This is what we were talking about earlier.

If the clutch is stuck, the AC stays in an unending cycle of always being one even when it is switched off.

And this causes your battery to die easily. In the AC compressor, you will also find connecting points where you can connect pipes to the refrigerant. Finally, there is a housing that contains valves, oil fill, and the compressor.

All AC compressors don’t look the same. In hybrid cars, we have electrically driven compressors. We also have rotary and reciprocating compressors. The most common type of AC compressor is the fixed swashplate.

What is the Role of an AC Compressor?

In the air conditioning system, the AC compressor works hand in hand with the refrigerant. In most cars, the commonly used refrigerant is usually a liquid that converts hot air into cold air.

The AC compressor compresses the refrigerant that absorbs heated air and turns it into cold air so that it can be sent through the AC vents.

Having said that the most common type of Ac compressor is the fixed swash plate, in such compressors you will find a pulley that is attached to the engine block.

This is the relay we have been talking about. This pulley is designed to be controlled by the AC buttons at the dashboard center console. The valves located near the compressor regulate the amount of refrigeration flow.

The AC compressor handles all these functions. And it also facilitates the absorption of hot air from the cabin which is then compressed and sent to the refrigerator so that it can be converted into cool air released through the AC vents.

AC Compressor Maintenance Tips

Even though issues such as a stuck AC compressor relay are hard to prevent, there are ways you can take care of this component so that it can serve you for longer. Here are some AC compressor maintenance tips;

  • It is crucial to always use the compressor so that all elements are well lubricated. This prevents the relay from getting stuck.


  • You also need to form the habit of making electrical checks on sensors, switches, and the clutch fuse. The latter is very essential.


  • Finally, if you have the time, clean the drive belts regularly.

Being a mechanical part, AC compressors won’t last forever. These tips contribute immensely to prolonging the life of your AC compressor. But with time, it will fail.

And as mentioned earlier, the best solution for a failing AC compressor is an immediate replacement. Lest you risk it draining your battery all the time.

And because not all of us are familiar with diagnosing and fixing AC compressor issues, it’s advisable to always have an expert replace a stuck AC compressor clutch.

Proceeding to do it yourself can be disastrous more so if you are not familiar with how AC components work.

What are the Signs of a Dying AC Compressor?

By now, you already know what a stuck AC compressor relay can do to your car battery. However, that is not the only warning sign of a dead or dying AC compressor.

Familiarizing yourself with these other features is essential as it helps you diagnose the problems early in advance. Below are common signs of a dying AC compressor;

  • The ac may not be as cold as it was. If you realize some temperature changes, then the AC compressor is on the verge of failing.


  • If you hear loud noises when the AC is on, that could be a sign of mechanical failure. Some of the components in the compressor may break and as a result, they may cause loud noises when the Ac is turned on.


  • A stuck AC compressor clutch. Another sign of a faulty AC compressor is a stuck clutch. We have already talked about the scenario where the AC clutch is stuck when the AC is activated. It can also get stuck when the AC is off. Meaning that the AC compressor doesn’t get power from the engine and so it won’t work at all.

Being on the lookout for the above issues can help you fix AC compressor issues sooner before they affect other car components.

Other than a Stuck AC Compressor Clutch, What Else Can Drain Your Car Battery?

There are many things in your car that rely on power coming from the battery. Most of these electrical components consume a considerable amount of energy.

You may not realize this when you use the electrical components when the engine is running. However, should you switch off your engine, there is a huge chance that they will completely drain your battery.

A dead battery can be quite inconvenient for many motorists especially if you have no option of boosting it.

Other than a stuck AC compressor clutch, here are other things that can drain the car battery;

  • The most common source of a drained battery is the parasitic draw.

As mentioned above, when the engine is switched on, the alternator recharges the battery. So it won’t be drained.

However, if the engine is switched off, indoor lights, car battery, a running AC, and other electronic devices drawing power from the battery will drain it completely if not switched off in time.

  • Headlights are also a contributing factor to a drained battery.

There is a reason why we are always advised to switch off the headlights before stepping off the vehicle. When the car engine is off and the headlights are still on, the battery will be drained completely.

  • Extreme temperatures can also drain old batteries.

New batteries are resistant to extreme weather. If you live in an area that’s too hot or cold and you happen to have an old battery. There is a good chance that you will always wake up with a dead battery.