Car Alarm Goes Off When Unlocking With Key – 6 Top Causes

I have been a driver for many years, and I have faced many car problems over that period. However, one of the most irritating car problems I have encountered is the car alarm going off. Whether I am in the house relaxing or in a traffic jam, the noise caused by the alarm is nerve-wracking.

In most of those cases, the car alarm went off because of a loud bang. Recently, my car alarm has been going off when unlocking using a key. After doing some research and finding out the reasons, I decided to share my results with you in this post.

So, if you ever come across a car with an alarm that goes off when unlocking using a key, here are the reasons why. Also, we’ll talk about how to fix them. So, get ready!

1. Set The Car’s Alarm Using The Key Fob

The first suspect should be your car security system. If you lock your vehicle using the key fob, you will have to unlock it using the same key fob. If you use a key to open it, the car will sound off the alarm.

This is a security measure as the security system will think that someone is trying to break in. Thanks to the dome light circuit that alerts you if the door is opened.

The key fob is specifically coded to the car and transfers an encrypted signal to open the car’s door. If you use the car key to open, this signal will not be detected; thus, the alarm will turn on. If you use the key fob to lock the car, unlock it using the key fob to avoid sounding the alarm off.

How To Fix It

Nonetheless, this issue can be fixed in a few easy steps. After you open the car using a key instead of a key fob, you can still stop the alarm. All you need to do is to place the key in the ignition and turn it.

Since the key has a Radio Frequency Identification (RFID) chip, the car will read it and confirm that the key is legitimate, which will automatically deactivate the alarm.

2. Overly Sensitive Shock Sensors

Another reason why your car alarm may go off when unlocking is because of overly sensitive shock sensors. Most aftermarket alarms work by sensing vibrations or shock sensors. Hence, these can sense when another car passes by or even a slight sound of a barking dog.

But if the shock sensors are extremely sensitive, then a simple touch as you attempt to open the car’s door may trigger the alarm. Also, when a goat or dog leans on your vehicle, this may sound off the alarm.

How To Fix It

Fixing a shock sensor is a simple DIY task. All you have to do is go through your user manual to locate the sensor. Then, configure the sensor by simply twisting it. Follow the instructions to the end to avoid making any mistake.

3. A Broken Microswitch

If your vehicle’s microswitch is broken, then your car alarm will be turned on every time you open the door. Note that every vehicle’s door is fitted with a lock cylinder. This is the system in charge of locking and unlocking car doors.

A microswitch is located on the back of every lock cylinder. On top of that, the microswitch is wired to the body control module. Additionally, it tells the body control module when you enter the car and alerts it to disarm the alarm.

So, if you unlock the driver’s side door and the alarm turns on, this is a sign that you have a broken microswitch.

How To Fix It

Fixing the broken microswitch is quite challenging as you have to remove the door panel. However, a technician or mechanic will have an easy time repairing the microswitch. So, it’s better if you have the mechanic fix the microswitch.

4. A Faulty Key Fob

If your key fob is faulty, this can also cause the car alarm to go off. You don’t need to press the key fob for it to sound off the alarm. This small gadget can send a signal just like that. A key fob is a device that locks and unlocks your vehicle. It is also referred to as the remote key.

How To Fix It

The good news is that it can be fixed quickly and straightforward. Start by replacing the key fob batteries. If it doesn’t work, reset the gadget to restore its normal performance. If need be, you may have to reconfigure the device.

5. Accidental Alarm

Perhaps you accidentally turned on the key fob in your pocket while opening your car using the key. The key fob has a panic button that can turn on the alarm if you press it accidentally. Most key fobs have a yellow or orange panic button.

How To Fix It

If you accidentally turned on the alarm sound, you can turn it off using the panic button. Alternatively, you may also turn off the panic button by starting and driving the car.

6. Low Battery /corroded Battery

It may be a sign that your car battery is running low. Car alarms are designed to alert the driver of a low battery. If you attempt to unlock your car using keys and the alarm turns on, this should be a sign that the battery is not low but dying.

Therefore, you should recharge your car battery as soon as possible.

If your battery is not low, then it may indicate that your battery is corroded. If it has rusty or worn-out terminals, the alarm will sound off. If not corrected, this may make the car’s electrical system to fail, with the alarm system included.

This is because your car’s electrical system may be confused and misinterpret the battery to have a low charge, which will also turn on your car alarm.

How To Fix It

Use a voltmeter to find out if the battery is low. If that’s the case, you can go ahead and recharge the battery. But if it’s the corrosion causing the car alarm to come on, you should clean the battery terminals using a battery cleaner. Remove the terminals and wear protective gear before cleaning.

See Also: Best 6 Terminal Removal Tool Kits (Review)

Bottom Line

If your car alarm goes off when you unlock it using a key, there is nothing to panic about. After looking at the possible causes and how to fix your car alarm, you should handle the issue fast.

But if you’re unsure what’s causing the car alarm to go off, you can take the car to a mechanic. You can go ahead and drive your vehicle peacefully without the annoying alarm sound.