Why Would a Car Alarm Keep Going Off & How Do You Fix It?

Car alarms are a great deterrent and a good warning system of someone trying to steal your vehicle. But what if your alarm goes off randomly and often? This can be a sign of a problem which you will need to remedy. Turning off the alarm is an option but then you have no protection against theft.

In this article we will talk about some of the possible causes of false alarms and how you go about fixing them. Not only is a constantly ringing alarm system frustrating, it can make your neighbors unhappy as well.

How Do Car Alarms Work?

We should probably start out by explaining how a car alarm is supposed to work before we touch upon reasons that it might go off at the wrong times. There are different types of car alarms but many work in the same basic way.

Generally speaking there will be a series of sensors around your vehicle including pressure sensors and motion detectors. When we arm our alarms these sensors are constantly monitoring for attempts to open or break into your vehicle.

If a theft attempt occurs an audible alarm will sound to both alert the nearby owner and try to scare away the would-be thief before they achieve their goal. Most modern alarms can be deactivated using your car's key fob if they sound for no reason.

A good car alarm system should also have an auxiliary battery to make sure it works even if the car battery becomes disconnected.

Why Would Your Alarm Go Off Randomly?

When working correctly your alarm should not sound unless something causes one of the sensors to record a potential threat. Unfortunately sometimes a fault can actually cause false alarms making your alarm sound and disturbing the peace and quiet for no reason.

Low or Dead Car Battery

As mentioned some of the best alarms have their own auxiliary battery power to serve as backup for the car's battery. If however they do not have this backup and the car battery gets a low voltage or dies then it can cause a triggering of the alarm for no reason.

If you had to wake up and turn off the alarm at some point in the night and then you wake up to a flat car battery this was likely the cause of the nocturnal disturbance. If the car starts fine then the battery is probably not connected to the issue.

A bad battery may need replacing which may cost a few hundred dollars but it is a simple enough repair. If the false alarm was caused by the battery then it should not happen again if you replace the battery.

Bad Alarm Control Module

This is not a common issue with factory installed car alarm systems as they have an integrated alarm control unit and a main electronic component, a control unit. If however you added the alarm aftermarket then you may find that a faulty control module is the problem.

This control module controls the sensors so if it fails then it can lead to false warning signals and as a result cause the alarm to sound. As mentioned it is not common but it can definitely be the cause of the issue if no other reason seems likely.

Overly Sensitive Sensors

It is always possible that the alarm is not necessarily false but perhaps is caused by an overly sensitive shock or movement sensor. In a factory fitted unit there will be presets for the sensitivity and even with an aftermarket set up you may be able to set how sensitive your sensors are.

If your sensors are a little too sensitive you might get an alarm going off by a cat jumping on your car at night or a drunk accidentally bumping into your car as they stagger home. These are not attempts at theft but the alarm has no way of knowing this.

Frequent alarms with no logical reason can be due to over sensitive sensors. You might be able to test this by activating your alarm and gently bumping against the vehicle yourself. If the alarm triggers then you may need to adjust the sensitivity or risk frequent false alarms.

Poor Alarm Installation

If the alarm system is new and just recently installed this can be an indication that it was not correctly installed. If mistakes are made in the installation this can cause the alarms to sound randomly for no logical reason.

If you had a mechanic do the installation go back there and explain the issue. They may have to double check their work and they should do this for free as it was their error. If you fitted the unit you may need to double check the install instructions and just make sure you got it all installed correctly.

Hood Latch Sensor

Professional car thieves will try and disable a car alarm to allow them to perform their crime undisturbed. This used to be possible by disconnecting the car battery removing the power needed to sound the alarm.

Modern vehicles are ready for this by having a hood latch sensor as part of the alarm system. If you try to force the hood open it will sound the alarm and the game is up. However dust, grime and debris can cause this sensor to become faulty.

It may simply need a clean or perhaps the sensor has become damaged and requires replacement. Damage to the sensor can be general wear and tear or the result of a failed attempt to get under the hood by thieves.

Fault in the Key Fob

The key fob in modern cars controls locking/unlocking of the vehicle, activation of the alarm and sometimes starting of the engine. This is a very handy device but if it starts to not work correctly you can have some issues.

If your key fob battery is dying or it has developed a fault you might find that it sends incorrect signals to your vehicle. This can sometimes result in sounding the car alarm for no good reason. This may be a simple fix if you only need a new battery but if the fob is broken you may need a replacement.

Door Lock Sensor

Another common issue might be related to one of the door lock sensors. This would be the same as the hood latch sensor in that it monitors for attempts to force the door open. If the sensor becomes damaged or develops a fault it may tell the system that there is an attempt at breaking in occurring.

What Should You Do if the Alarm Keeps Sounding?

Constant unnecessary sounding of the alarm gets old really quickly and if it's annoying you then you can bet your neighbors will be even less patient. Not using the alarm is an option but not a great one so your best bet is to get to the bottom of the issue quickly and get it fixed.

Check the Trouble Codes

When the car alarm goes off it will create trouble codes that are recorded in the car's computer. These codes can be retrieved and read using an OBD2 scanner tool. You simply plug this scanner into the OBD port which is usually somewhere below your steering wheel and run a diagnostic.

Using the list of codes and their meanings from your user manual you may find out exactly where the alarm issue is coming from. This will allow you to know what steps you may have to take to fix the issue. It is important to note however that this will only work for factory alarm systems not aftermarket setups.

Charge or Replace the Battery

If the problem is related to a low power or dead battery then the fix is simple. Lights left on overnight may have drained the battery so recharging the battery may fix the issue. Hopefully the recharge will hold and you should have no further issues.

Batteries do wear out over time however so if the unit is no longer holding a charge you may need to replace the battery itself. There are also some other issues such as the alternator which can affect battery charging that would indirectly be the cause of the alarm going off.

Clean and Lubricate Hood and Door Latches

If the issue relates to a latch sensor then you can possibly fix the issue by removing dirt and debris from the door and hood latches and also giving them a little spray with WD40. This will ensure the latch is working fine.

If the sensors have become damaged however you may need to replace these.

Check Your Sensitivity Sensors

If you have a factory fitted alarm system you may be able to use a scanner tool to both read what your sensitivity settings are and also adjust them if they are too high. This will allow your shock and movement sensors to only trigger if there is the likelihood of an actual attempt to gain access to your vehicle.

You may also be able to set the sensitivity on your aftermarket alarm systems as well. This will of course depend on the type of system. In more advanced cars you may even be able to access the sensitivity settings through your vehicle's touch screen.

Fix the Key Fob

If the key fob is at fault and sending wrong messages to your car then you may need to change the battery or replace the unit. This can be easy but sometimes you may need to reprogram the key fob after a new battery and definitely if it’s a new fob.

It can be difficult to reprogram key fobs especially in newer cars, basically for security purposes. You therefore may need the help of a mechanic or a dealership that works with your make of car.

Conclusion

A car alarm that gets set off at the wrong times can be frustrating and cause a disturbance in your neighborhood. This is why you will want to get the issue dealt with quickly. It may be a very simple fix or something a little more complicated.

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