Car Alarm Keeps Going Off – How to Fix Faulty and False Car Alarms

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Car Alarm Keeps Going Off

Having False Car Alarm Issues? Read this!

A car alarm that keeps going off at the slightest provocation is as annoying as a jackhammer at full throttle. This problem is most likely caused by aftermarket car alarms that haven’t been installed properly. I had a problem similar to this when I bought a used Mitsubishi Galant. The stock factory alarm was overridden to accommodate an aftermarket alarm. That car would keep on blaring the alarm day in and day out. I knew something had to be done.

Hey, Matt here. Want to know what triggers car alarms? Keep reading.

The day finally came when the battery was too weak to start my car. I had to buy a new battery only to have the alarm drain all the power again in less than a week. I drove to the nearest garage to have the problem fixed. I wasn’t looking to restore the functionality of the alarm. All I wanted was to pull a fuse or disconnect a wire that will get rid of the problem forever.

You know what, all it took was a couple of minutes to locate the main alarm fuse under the console. My mechanic friend simply pulled out the fuse and the alarm was dead, permanently! Also gone was the equally annoying flashing LED light indicator of the alarm that would blink intermittently as I drove, even if the alarm was disabled (related: how to disable a car alarm). Imagine my relief when I had to waste money on a brand new battery when all it took was a simple fuse removal.

My experience with various make and model of cars was enough to inspire me on writing a piece on the reasons why a car alarm keeps going off. I will also share a couple of tips on how to fix faulty car alarm problems.

Where to start?

We’ll discuss some of the reasons for a false vehicle alarm, but first I wanted to share with you my favorite tool for diagnosing the alarm. It’s called an OBD2 Scanner. Simply plug it in to your vehicle’s OBD2 port, and it’ll tell you what the problem is! Here’s some links to get you started


Why does my car alarm keep going off?

Believe me when I say this problem can be caused by a barrage of reasons, of which some can be difficult or tricky to explain. Most problems with vehicle alarms are caused by installing after-market alarms that haven’t been wired or grounded properly. I only encountered problems with the factory car alarm when the key fob is subjected to shock or when the control unit is running low on juice.

Here are the many reasons that can cause the false alarms intermittently and unexpectedly:

1. Faulty key fob or malfunction

I have a habit of lowering the front windows every time I start my car. I learned this lesson the hard way. There was a time when I accidentally dropped my keys along with the key

Faulty key fob

fob before I started my car. I pushed the unlock button and everything seemed fine. I started the engine and it fired right up. I left something in the garage so I went out and slammed the door shut. To my horror, the alarm engaged to LOCK which essentially locked my vehicle with the engine running and the key inside the slot. Wow.

I had to hire a locksmith to open the doors in my vehicle. There was nothing I can do while the car was idling quietly as I locked myself out. Hence the reason why I developed the habit of lowering the front windows before starting the vehicle.

The moral of the story is to never drop the key fob of your vehicle. If you do, make sure everything is working fine before starting the engine. While the key fob did not trigger a noisy blare of the alarm, it malfunctioned just enough to cause a bigger problem. If you notice anything wrong with the key fob, bring your car to the dealership immediately. You might need a brand new key fob. In most cases, the key fob might have a weak battery. All that is needed is to replace the battery and you’re all set.



hood latch sensor


2. Problems with the hood latch sensor

Ever wondered how the car alarm knows when an entry point in your vehicle is breached? There are a variety of sensors located in the hood, trunk, and doors of your vehicle. The sensors in the doors and trunk are not prone to having problems, but it’s a different story with the hood latch sensor. Depending on the make and model of your vehicle, the hood latch sensor is located in the engine bay above the frame of the headlights. The sensor can trigger a false alarm if filled with dirt, grease, and debris.

On some models, the hood latch sensor is a spring-driven device. Dirt and grease on the springs will severely affect the performance of the sensor. If you find out the hood latch sensor is dirty, use a soft bristle brush and some soapy water to clean the sensor. You can also spray the sensor with some WD-40 to protect the sensor from rust and corrosion.

There are times when the problem can be caused by a bad connection. Check the hood latch sensor and trace the wiring back to the main connection. Make sure the contacts are clean and free from damage. In most cases, simply disconnecting and connecting the wiring might solve the problem. This especially holds true for vehicles that were involved in a crash or collision.

If your car was the victim of a crash (particularly in the front) and the alarm keeps going off, it might have something to do with a broken or misaligned hood latch sensor. If the car was damaged in the rear, make sure to check the sensor in the trunk as well.

Sensitive shock sensor

3. Sensitive shock sensor

If your car alarm is too sensitive to slight shock, it will keep going off and eventually drain the battery. The shock sensor in most can be configured by simply twisting a knob. If you’re not sure how to do this, check the owner’s manual. If your vehicle is fitted with an after market alarm, make sure to read the instruction manual to know how to adjust the shock sensitivity of the unit.

4. Weak or dead car battery

Some systems are designed to detect low battery levels. Attempting to start the vehicle with a dying or weak battery will usually trigger the alarm to go off. The car alarm in a modern car needs a consistent supply of power to run effectively. If the battery is weak, this can cause a myriad of problems. Check the voltage levels in your car battery using a handy voltmeter. However, if you are wary about this procedure, simply bring your car to a professional mechanic for some much needed help. It may be time to charge the battery at the mains, or you may have to buy a new one instead.

5. Various electrical problems

Electrical problems, faulty wiring, and short circuits can wreak havoc on the alarm system in your car. My friend used to have the same problem even though there was nothing wrong with the vehicle. All the sensors were working fine but the false car alarm would keep blaring in the middle of the nights. As it turns out, his vehicle had a grounded alternator. For some strange reason, this problem is the reason why the alarm kept going off.

How do I stop my car alarm from going off?

There are many ways to do this:

  • You can try inserting the key into the lock, unlock the doors, and lock it once more to shut down the alarm. If the door is locked, unlock it and lock it again. The action might be enough to shut off the siren.
  • Try pressing on the key fob to unlock the door. If the alarm doesn’t respond, check the batteries in the key fob. If the door unlocks and the alarm starts blaring once more, it is better to have your vehicle checked by a mechanic or electrician.
  • Check the owner’s manual. You might need to perform some steps to reset the computer which will also reset the alarm.
  • If all else fails, it is time to remove the fuse. Again, you will need the owner’s manual for this. If you disconnect the fuse, you might also lose the central locking function in your vehicle. Again, if you’re not sure, never hesitate to consult a mechanic. For vehicles equipped with aftermarket alarms, you will need to locate the main alarm fuse (which is connected to the battery) to disable the alarm system without disabling the central locking function.

car alarm system drain the battery

Can a car alarm system drain the battery?

Yes. Anything that consumes power will have a chance of draining the battery in your vehicle. A vehicle alarm that keeps going off will eventually weaken or permanently damage the battery. You might be surprised to know that car alarms only consume a very small amount of power (usually 0.5 watts) but repeated engagement of the siren will nevertheless consume a lot of power in the long run.


Car alarm keeps going off? This is a huge cause for concern. The car alarm problem will not only affect the battery, but it will also annoy your neighbors. Make sure to have the alarm system checked to rectify the problem at the soonest possible time.

Main image source: Paul

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