Why is my car alarm going off randomly? This is how you fix your car alarm.

People often report hearing their car alarm ringing unintentionally. Even worse is the problem at night, when many people sleep. Then suddenly your alarm will go off without explanation.

What is the reason for this? This isn't a theft alarm. It can also happen due to poor installation, or any other reason. Is it a random car alarm?

Low battery or incorrectly calibrated movement sensors are the most common reasons why your car alarm continues to go off. A faulty door lock sensor or hood latch sensor can cause the alarm to go off.

Now when you got a quick look at the most common reasons, let’s take a look at a more detailed list of the 7 most common causes why your car alarm keeps going off:

Here are seven common reasons your car alarm keeps going off randomly

1. Low battery charge or dead car battery

Low battery charges or a bad car battery can cause an alarm to go off in your car at night. A bad car battery can cause your car alarm to go off in the middle of the night.

If your car alarm is going off, but you can still start your car without issue, it is most likely something else faulty.

To check the condition of your battery, either use a tester for car batteries or simply a multimeter. You will be able to replace any that are defective.

2. Sensitive Motion/Shock Sensor

The alarm will sound even when a small animal or cat touches the car. The car alarm you choose depends on the make and model of your vehicle. alarm system Installed in your vehicle or an alarm system from the manufacturer.

In some car models with a car alarm from the factory, you can program the shock and movement sensors’ sensitiveness with a Diagnostic scanner.

It is very common to need this on Audi and Volkswagen cars, as their sensors can be over-sensitive and may go off at times.

Many aftermarket car alarms have adjustable sensors. You can find more information in the car alarm manual.

3. Sensitivity to Faulty Hood Latch

Modern vehicles have a hood latch sensor, which triggers the alarm if someone tries to force open your car’s hood.

Depending on your car’s condition, very likely dust, grime, and debris will collect where the hood latch sensor is located, and this causes the alarm to go off.

This problem can be fixed by finding the sensor and cleaning it. The sensor may have been damaged or tampered with, if you still hear the alarm sound. You can replace the sensor if it is damaged or tampered with.

The hood latch sensor is usually located inside your hood lock, however it may also be found externally.

4. Failure to Install Door Lock Sensor

Your car alarm also monitors the door locks to ensure that nobody opens your doors.

A faulty sensor on the door can set off an alarm and cause it to sound. The door latch sensor can be found inside or outside the lock.

It can be difficult to find the problem door latch sensor if it happens occasionally.

The door latch sensor typically has two wires. One is an open circuit for when the door opens and the other is closed when the door closes. This allows you to easily identify the door latch sensor. Measure with a multimeter.

Door actuators can be found inside doors, making it difficult to measure them if not measured from the control unit.

5. Failure of the Key Fob

You can use the key fob (also known as a remote key for your car) to lock or unlock your doors, and start your engine using a single button press.

Since the key fob also has controls linked with the car alarm system, a malfunctioning or faulty key fob can send an incorrect signal, which may trigger the car’s alarm.

To fix the issue, you can either replace or reset your key fob battery. If you've replaced your batteries but have problems with communication, it may be necessary to reprogram the key fobs.

6. The alarm is not correctly installed

You may have an incorrectly installed car alarm system if your alarm goes off after you've recently replaced it.

Let a mechanic install the item. If it wasn't installed properly, you should go back to your workshop and describe what happened.

7. Bad Alarm Control Module

Installed car alarms from the factory usually have an integrated alarm controller unit and a main electrical component control unit. A faulty control module, however, is rare.

Aftermarket car alarms often have an alarm control module. This module controls the sensors and switches and can cause alarms to go off occasionally.

How to deal with a car alarm that keeps going off

It can be difficult to fix a car that isn't turning off, but there are some tricks you can do to try. Some of these require special tools. You can find the steps here.

1. Charge the battery & Check the charging voltage

First, you will need to test the voltage of your battery using a multimeter. The voltage should range from 12 to 12.5 V when the ignition switch is turned on. If it’s under 12 volts, it is definitely time to recharge the car battery with a battery charger. Charge it fully for 24 hours to ensure it’s fully loaded and see if the car alarm keeps going off anyway.

If the alternator works properly, a car battery shouldn't be discharged if it is being driven every day. Turn the engine on, allow it to run and then, at idle, check the battery voltage using a multimeter. If everything is working properly, it should read 13.5 to 14.5 V at idle. If it’s not – you may have a bad alternator which is causing the car battery to drain.

A bad battery could be causing voltage drops to below 12 V at the ignition. This is even when the alternator charges.

2. An OBD2 scanner can be used to check for trouble codes

You can check for trouble codes using a scanner tool if everything is fine. Either borrow one from someone you know, or have a professional scan the codes. It will take more than a cheap scanner to find trouble codes for your car alarm. They can't read the trouble codes directly from the engine control module.

Also, if you have an aftermarket car alarm, you can’t check for any trouble codes in the car alarm system with a standard scanner. If you do find trouble codes in your car alarm system, it is important to troubleshoot the issue immediately.

3. Lubricate all door hatches & locks

You can also lubricate the door locks and the trunk latches with a grease to make sure they close correctly. Spraying some cleaner in the connectors is a great idea if you are able to reach them. It can sometimes be very difficult to access them without disassembling the car.

4. Make sure you are using the correct sensitivity settings

A factory-installed car alarm can have sensitivity settings that affect the movement or shock. This is something that can be done only with the best scan tools. The cheaper models will have a hard time doing this. In some car models, you can reach these settings from your car’s display settings so therefore it’s good to check the owner’s manual for any sign of these settings. You can reduce the sensitivity if you are able to locate them.

5. Replace the battery in your key fob

To ensure that your key fobs are properly charged, the last thing you should do is replace their battery. This issue is unlikely to cause your car alarms to go off but it does happen occasionally. Most keys have key fob batteries that are relatively inexpensive and easy to change. Again – check your owner’s manual for instructions on how to replace the key fob batteries.

Even if all the above are unsuccessful, a deeper diagnostic understanding is necessary to determine why your car alarm keeps going off. Therefore it’s time to use professional help from a workshop with the proper diagnostic tools.

FAQs about Car Alarms