Car Alarm Keeps Going Off After Battery Change – (Fix Guide)

The car alarm system is quite convenient for car owners to protect their car and its parts from electronic thieves. Alarms operate by drawing power from batteries, which requires battery replacement. But you may notice the alarm stops after replacing the battery.

Usually, when you change the battery, it can come loose or damage the wire connections unwantedly. Besides wiring, improper battery installation, issues with key fob function, faulty sensors, etc., are also responsible for this issue.

Fortunately, these problems aren’t challenging to fix. Read on to understand car alarm functions and common causes of these alarm problems, and how to fix them quickly.

Understanding The Function of Car Alarm

Car Alarm Keeps Going Off After Battery Change

You should have basic knowledge of your car’s alarm functions before attempting to troubleshoot the issue behind the alarm goes off when changing the battery.

Most car models feature alarms connected to the car’s trunk sensors and door. Here are the standard alarm functions:

Alarm Control UnitThis component is also known as the “Brain.” It controls and commands the whole alarm system.
Alarm SensorsIt can be set in different places depending on the car model. However, alarm sensors are mostly located underneath the dashboard, pressure sensor, and window sensor.
Alarm TransmitterThis function is included on the remote or key fob for manually turning off the alarm.
Alarm SirenIt’s a warning siren, which is mostly connected to the car’s stereo.
Alarm WiringElectrical wires are connected to fuses, sensors, and other components that can be stolen easily. These wiring connections are set to propagate signals to the alarm.

Common Issues Behind Car Alarm Keeps Going Off After Battery Change

The alarm wiring is directly connected to the car’s battery from where the alarm gets the power to operate. Therefore, changing the battery can turn off your car’s alarm system.

Here’s a list of 5 common reasons why changing the car battery turns off the alarm:

Common IssuesQuick Solution
Wiring problemInspect all the connected alarm wires thoroughly and fix the defective one
Inaccurate battery installationDisconnect and reconnect the battery properly
Defective alarm control unitSearch for the defective element in the unit, then fix it
Issues with the key fobReset and sync the key fob
Faulty sensorRecalibrate alarm sensors

We’ll discuss these issues and quick solutions in detail in the following discussion.

1. Wiring Problems

Car alarms operate by using electric power through wires. Some wires are connected to the battery.

Therefore, when you remove and install a new battery, the wires can get loose or damaged accidentally. Consequently, the alarm fails to receive electric energy to operate functionally.


  • You first need to track down the faulty wire by inspecting each wire carefully.
  • Consider tightening all the wire connections while you look for the faulty wire.
  • Once you find the damaged wire, fix or replace it to solve the problem.

2. Inaccurate Battery Installation

Since your car battery is the primary energy source of the alarm, inaccurate installation of the new battery can cause this alarm issue. This scenario is common with new owners.


  • First, disconnect the battery, then reconnect it following the instructional manual.
  • Now unlock your car doors and connect the wires to the battery and see if it fixes the problem.

If it doesn’t solve the problem, consider getting help from a professional to install the battery correctly.

3. Defective Alarm Control Unit

We mentioned that every car model comes with an alarm control unit to command the entire system using remote or other devices.

After changing the battery, you may face some power functioning problems in your vehicle, which also affect the alarm control unit. However, this particular issue behind the alarm going off is rare but possible.


If the control unit is causing this problem, you first need to ensure that all the wires in this compartment are functional and provide enough voltage. And if the wires and voltage level are right, consider fixing the other elements in the control unit.

4. Issues With The Key Fob

This is probably the most common issue behind the alarm going off after changing the battery.

When you lock your car using the remote key fob, it activates the security system of your car. Hence, when you unlock the car with a key, it triggers the car alarm. That’s why some users keep the alarm off using the key fob.

Changing the battery can malfunction the key fob and prevent it from programming functionally. Your car’s ECU may not recognize the codes sent by the key fob when it’s malfunctioned.

Therefore, when there’s a problem with the key fob, your car alarm may stop responding to the commands sent by the key.


To fix a malfunctioning key fob, you need to reset it. The traditional way of resetting a key fob is to insert the key in the lock and keep locking and unlocking the door with the key to sync it with the car.

Then switch on the car, insert it into the ignition, and turn on the key fob. This step will help the ECU to recognize the key fob. You can also follow a YouTube tutorial on this.

5. Faulty Sensor

Car alarms include multiple sensors to receive signals and alert the driver. Therefore, having a faulty sensor means your car’s alarm won’t receive signals. Consequently, it won’t function as it is supposed to.


There are two types of alarm sensor control that you need to fix to solve the problem: DIP switches and Rheostat. DIP switches are in charge of maintaining electricity to keep the alarm system functional.

And Rheostat comes with a bolt that works to adjust the resistance and sensibility of the alarm. Therefore, tightening and fixing these sensors should solve the sensor problem.


So you now know the typical reasons why the alarm goes off when changing the battery. Though this is an irritating situation, fixing this issue isn’t a tricky task.

You first need to find out the main culprit behind this issue and then try to fix it using our methods.

If you fail to find the main reason or solve the problem by yourself, don’t take risks and seek help from professionals to fix the alarm without causing further damage.

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