7 Causes of a Car Alarm That Keeps Going Off (and How to Turn It Off)

If you’ve ever had a car alarm that won’t stop going off, then you know how frustrating it can be. They can start in the middle of the night for seemingly no reason at all, or even worse, they can start going off while you’re driving down the road!

We understand your frustration, and we want to help you get to the bottom of it. That’s why we came up with this comprehensive guide to walk you through everything you need to know to fix the problem for good.

How a Car Alarm System Works

Before we start diving into all the potential reasons your car alarm might be going off unexpectedly, you need to have a basic understanding of how these alarms work in the first place. There are multiple generation car alarms, but they all have some or all these features.

First, just about every car alarm out there connects to your door and trunk sensors. This helps because if someone up to no good picks the lock, smashes out the window (to unlock the car), or simply opens the door or trunk by any other means, you want the alarm to let others around know that something is wrong.

car thief setting off alarm

When you unlock the car with a key fob, it disables the alarm. But if they manage to get the car unlocked without a key fob, it can set off the alarm. It’s also why the alarm goes off if you lock the vehicle from the outside and someone inside the car unlocks it and gets out!

Another sensor alarm systems use to set off the alarm are shock sensors. Not every car has a shock sensor, but if your vehicle has one, then it can help prevent some car thefts. Shock sensors work by detecting impacts to your car.

This can happen when someone runs into your car or when someone smashes out a window. This matters because with a traditional car alarm system, they can smash the window and take out whatever they want. As long as they don’t open the door, the alarm won’t go off!

Shock sensors give you an extra layer of protection. They can also go off if someone is in the process of picking the lock on your car. It’s nice to have the alarm go off before anyone even tries to get in!

Why a Car Alarm May Be Going Off Randomly

There are more than a few reasons your car alarm might be going off more than it should. Below we’ve highlighted seven reasons your alarm might be acting up.

#1 – Dead Battery

bad car battery symptoms

It might not make much sense to you right off the bat, but a low or dead battery can create a ton of odd problems for your vehicle. It’s not unheard of for a battery with a dead cell or other electrical malfunction to set off the car alarm.

If the alarm keeps going off and you find your vehicle needing more jumpstarts than usual, then you should check out the battery.

Related: What Causes a Car Battery to Keep Dying?

#2 – Key Fob Malfunction

key fob

One of the most common reasons for a car alarm that keeps going off is a malfunctioning key fob. The key fob is a manual way to set off the alarm, so if there’s something wrong with it, then it can easily set off the alarm when you don’t want it to.

If you suspect the key fob might be the problem, try replacing the key fob battery and see if the alarm keeps going off. Alternatively, some key fobs are able to be reset. Check your car manual or contact the aftermarket alarm manufacturer for reset instructions.

#3 – Blocked or Damaged Sensors

car alarm door sensor

Your car alarm uses various sensors to alert you of a problem. So, it makes sense that if some of those sensors aren’t working the way they should that your car alarm might keep going off.

Blocked or damaged door or trunk sensors are a common culprit of a repeat car alarm malfunction.

#4 – Wiring Issue

damaged wiring

Everything in your car alarm uses electricity, and all that electricity runs through wires. When everything is working as it should, there aren’t any problems. But if some of those wires get damaged, start to cross, and electricity goes to the wrong place, then your car alarm might keep going off.

Wiring problems are tricky to track down, but if you can find the fault, they’re usually pretty straightforward to fix!

#5 – Over Sensitive Sensors

alarm shock sensor

In addition to door and trunk sensors, your vehicle can use shock sensors to set off the alarm. These sensors have various sensitivity levels to trigger an alarm. The most sensitive sensors out there will go off if even a cat brushes up against it.

If you have overly sensitive shock sensors, you might be able to adjust them yourself, or you might need to take them to a dealership.

#6 – Faulty Control Unit

car alarm control unit

Every sensor that’s a part of your vehicle’s alarm system reports to an alarm control unit. While it’s rare for these units to act up, it’s not impossible.

If you’ve ruled out all the sensors and you’re sure the right voltage reaches the control unit, the unit itself might be your problem.

#7 – Incorrect Installation

faulty car alarm installation

If you just got a new aftermarket alarm system and it keeps going off, there’s a good chance something’s not hooked up correctly. It can be as simple as a crossed line or a missed sensor. Double-check the installation process or take it back to the installers!

How to Turn Off Your Car’s Alarm (When a Key Fob Doesn’t Work)

It’s all nice and good to try and fix the car alarm, but when you just need it to turn off and the key fob isn’t working what can you do? Well you’re not completely out of luck. Below we’ve highlighted four potential fixes.

The first two are the easiest but don’t always work, but the last two will shut your car alarm up every time.

#1 – Start the Car

start car

When your car alarm is working the way it should, it should stop going off as soon as you start the car. That’s because your car’s ignition system has an anti-theft device. If your car detects you’re the right person trying to start the car, then there’s no reason for the alarm to keep going off!

But for some older cars, this won’t always work, and if the control unit is the problem, it might keep going off even while driving.

#2 – Lock and Unlock the Car

car alarm keeps going off

Sometimes this is all you need to do to reset the alarm system and shut the alarm up! Lock the car and unlock it, and many car alarms will stop going off.

Once again, this isn’t foolproof, especially if the control unit is the problem. But it might reset the system and give you some peace and quiet.

#3 – Remove the Fuse

blown fuse

If the first two fixes don’t shut off the alarm, this is probably your best bet. Your car alarm system runs through a fuse to protect the circuit, and if you pull the fuse, the alarm doesn’t have any power. No power means no alarm!

Even better, since the alarm circuit is the only thing you cut power to, everything else in your car should work just fine. The only difference is now that you cut power to the alarm system your vehicle doesn’t have any sort of car alarm.

It’s up to you to decide if it’s worth investing the money to fix the alarm and give your vehicle and your belongings inside a little extra protection.

#4 – Disconnect the Battery

how long does a car battery last

If you can’t track down the right fuse or need to shut the vehicle up faster, another foolproof way to cut the alarm off is to disconnect the battery. Disconnecting the battery removes the electricity from all the circuits in your vehicle, and that’s sure to kill the alarm.

The only downside is now you can’t move your vehicle either. No car battery means no power to anything, and that can be a pretty big deal if you still need to use your car while you figure out the car alarm problem.

Adam Mann


  1. alarm goes off at random when car is locked. Sprayed WD 40 on hood latch. That worked for 2 days, when it went off again. Any ideas?

    1. I wonder if there is a way to scan the vehicle to see what triggered the alarm. Perhaps a sensor is malfunctioning or there is a short somewhere.

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