Car Alarm Keeps Going Off: Why and What to Do | Drivetrain Resource

Drivetrain Resource

How to Fix a Car Alarm that Keep Going Off

Car alarms are designed to detect potential intruders in order to protect your vehicle and its contents. However, it is not uncommon for a car alarm to go off, or keep going off,  for no apparent reason– also known as false alarms or “nuisance alarms”. 

In this article, we will discuss some of the common causes of nuisance car alarms and what you can do to diagnose and prevent them.

The first thing you should do if your car alarm keeps going off is block the signal from your key fob and see if that stops it.

Table of Contents

Car Alarm Going Off Causes

While there’s a lot to car alarms, when they randomly go off, it’s usually a sensor issue or the alarm is receiving a panic signal from the fob when you aren’t pressing any buttons.

Key Fob

ALarm Keeps Going off at random

A worn or damaged key fob can cause your car alarm to go off at random. To prevent this from happening, check your key fob periodically and replace it if necessary.

The best way to check your key fob is to take it far enough away from your vehicle that they can’t detect one another anymore.

Faulty Sensors

Alarm going off randmomly

A faulty or damaged sensor is one of the most common causes of nuisance car alarms. 

A car alarm’s sensors are designed to detect motion, vibration, and shock, so a defective or old sensor may trigger a false alarm if it is not able to sense correctly. 

The best way to determine if a sensor is causing your alarm to go off is to test each one individually.  Car alarm systems have a combination of the following sensors (older cars will use less).

  • Motion Sensors
  • Vibration Sensors
  • Door lock sensors
  • Shock Sensors
  • Magnetic Switches
  • Ultrasonic Sensors
  • Laser Detectors
  • Hood latch sensors

Door Lock Sensor

Of these sensors, the most common issue is with the door lock sensor.  It tells your vehicle alarm controller whether or not the door is locked.  It’s usually connected to or part of the power door lock actuator.  

If your vehicle’s alarm keeps going off when you open the door (and the security system is unarmed), the door lock sensor still thinks the doors are locked.

Also, some vehicles don’t like to be opened with their key at all. Using the unlock button on the key fob will likely remedy the situation.

Hood Latch Sensor

Your car’s hood latch sensor is designed to detect whether the hood is open or closed. If this sensor malfunctions, it can trigger a false alarm. To prevent this from happening, make sure to inspect the hood latch periodically and replace it if necessary. 

Due to where a hood latch sensor lives (under the hood), it’s common for it to get dirty.  Try cleaning the hood latch and sensor (you should see a sensor with wiring right by the hood latch).

Low Battery

Another common cause of car alarms going off randomly is a low battery. A weak, dying, or dead battery may not be able to power the alarm’s sensors, resulting in false alarms.

The only way to know if a weak battery is causing the alarm to malfunction is to have it tested. Any local parts store should be able to test and replace your battery if it’s needed.

Wiring Problems

If the wiring of your car alarm is not properly connected or insulated, it can cause false alarms. To prevent this from happening, have a professional inspect and repair any faulty wiring, particularly if you are using an aftermarket alarm.

Interference from Other Devices

Modern devices such as smartphones and Bluetooth speakers can interfere with your car alarm’s sensors, resulting in false alarms. To prevent this from happening, make sure to keep any potential interference-causing devices at least 10 feet away from your car alarm.

Incorrectly Installed Aftermarket Alarm

If you have installed an aftermarket alarm system in your car, it is possible that it was not properly configured. This can cause the alarm to go off for no reason at all.

To prevent this from happening, make sure to follow the installation instructions carefully and have a professional install the system if necessary.

How to Fix a Car Alarm that Keeps Randomly Going Off

If your car alarm keeps going off randomly (as in the middle of the night), getting it fixed before your neighbors decide to disown might not be a bad idea.

Here are some steps you can take to fix the issue:

  • Check the batteries in both your vehicle and key fob. Replace if necessary.
  • Inspect all sensors and replace any that are damaged or worn out.
  • Check for any potential radio frequency interference from nearby devices.
  • Try blocking your key fob from talking to the vehicle.  You can use aluminum foil and put the fob as far from the house as you can.  If the alarm stops going off, leave one key fob out until you figure out which key fob is malfunctioning.
  • Have a professional inspect and repair your car alarm system if needed.
  • Set up a game camera, or camp out to see if anything sets off the alarm.  It could be that you have a sensitive sensor, and an animal is setting it off.

If you are positive that nothing is setting off the alarm randomly, check your owner’s manual for how to disable the alarm system if you can live without the added vehicle protection


If your car alarm keeps going off, it is important to determine the cause of the false alarms in order to prevent further issues and protect your vehicle. By examining the above common causes and taking the necessary steps to fix them, you can help ensure your car alarm is working correctly.

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