Why do alarms stop working when the vehicle is unlocked with a key? What causes the alarm to go off when opening the vehicle? Is the warning device not there to prevent the car from being stolen?
A car’s alarm is a valuable device as it not only warns the vehicle owner that their car is being tampered with but also reduces the possibility of car theft.
Although, for some reason, these vehicle alarms are very loud and can make the car owner frustrated at some point, especially when the notice refuses to stop.
Vehicle owners should also be aware that these alarms can go off anytime without any good trigger. Furthermore, any alarm may go off for many reasons, like a low battery, wiring problems, bad sensors, or a malfunctioning key fob.
This article covers all the possible reasons that may cause the alarm to be triggered when opening the car with a key. In addition, we will also look at possible solutions.
Introduction to Car Alarms
Usually, the basic settings for all types of cars are all similar. Detectors or sensors can be found at almost every point in the vehicle.
All these sensors collect data from all over the car and send it to the vehicle’s brainbox or processing unit (the vehicle’s ECU) or maybe a dedicated processing unit for the alarm systems within the car.
When a key fob sends a signal, a receiver within the vehicle receives the signal and tells the car’s loudspeakers(usually powered by the car battery) to sound the alarm when it perceives danger or threats.
In rare cases where the thief is smart enough to cut the car’s battery wires for a quiet operation, there is no need to worry because there is usually a backup source of power that the alarm system is designed to use.
Whenever a security sensor sensed a voltage drop, it could set off even the most straightforward alarm. For example, opening a door or simply detaching an electronic clamp that holds a trailer to the vehicle can cause the car’s alarm to start blaring.
Working Principle of Car Alarm
Usually, alarms produce high-pitched sounds meant to alert the car owners of an intended act of theft, and if the owners of the cars are not nearby, the noise made by the alarm can chase the thief away.
Alarms in a car are an excellent way to prevent theft, but you have to understand that there are scenarios where the alarm may sound even when there has not been an attempt to steal your car or break into it
In most recent models of the vehicle being manufactured, the alarm system comprises many sensors, a receiver tuned to the frequency of your key fob, loudspeakers tuned to the code of your key, and a processing unit.
Whenever one or more sensors within the car’s alarm system sense any irregular activity, like a sound above normal levels, vibrations from objects falling on the car or beside it, or the vehicle moving with its engine off, it could cause the alarm to sound.
The alarm will continue to sound very loud until an authorized person can stop it by turning the alarm off or reconfiguring the alarm settings. Before an alarm in perfect working condition goes off, something unusual must have occurred.
Why Does my Car Alarm Go off When Unlocking With Key
One of the major common reasons is an entry key fob with a low or dead battery. When key fobs are used over long periods, the batteries can go flat. If that happens, the fob might not be able to send signals correctly, which can cause the alarm to sound.
In this part of this article, we will be discussing some possible reasons why your car alarm can go off irregularly. Here are some reasons:
1. Your Battery is Low
There is a problem with a vehicle’s battery if the vehicle alarm inexplicably goes off at midnight and one wakes up to a battery dead. The battery is not only slow, but it is also the cause of the annoying anti-theft warning.
Unknown to some vehicle owners, vehicle alarms also help alert drivers when the battery is getting low. Therefore, starting a vehicle with a dead battery immediately triggers the alarm.
Therefore, do not fear the next time an alarm goes off when a vehicle is started. Check the operating voltage using a voltmeter. It may become necessary to shock or completely change the battery if it reads below 12.6V (or any voltage recommended in the owner’s manual).
2. There May Be Problems in your Wiring or Circuit
Another issue requiring investigation when an alarm keeps going off is wiring, which relates to sensitive sensors. Sometimes, the problem is not with the battery, key fob, or sensors. Instead, a section of the electrical cable connecting these parts could be damaged or loose.
Find associated symptoms to confirm if this is the cause of the problem. If the alarm goes off repeatedly with the horn and headlights flashing, it might be a wiring issue. Otherwise, another source could be the alarm’s trigger.
3. Bad Alarm System
Security systems can also be their problem, especially if not installed correctly. Many car owners do not have 100 % confidence in the level of security which Factory-fitted alarm systems offer. Therefore most car owners prefer to go for aftermarket alarm systems that they can customize to their preferences.
Now, most aftermarket alarm systems are sometimes poorly installed, especially when the installation is done through a DIY process or at a poorly equipped garage. One way to know that the alarm installation was not correctly done is if the car alarm keeps going off at a particular time. For example, if the alarm keeps going off at night.
If professionals installed the alarm system, you could always return to their workshop for troubleshooting or reinstallation.
Also Read: Is Your Keyless Remote Battery Low? (Here’s What To Do)
4. Your Door Lock Sensor Might be Bad
Usually, if a vehicle’s door is not closed correctly, it could malfunction the alarm system. The alarm may be triggered if the alarm system senses that the door is locked incorrectly.
The door lock sensor is the device that confirms whether the door is locked or not. It is found within the door lock actuator—these sensors, due to their design, malfunction when water enters the actuator housing.
Excess moisture in the doorlock actuator can also lead to short-circuiting, causing faulty sensor wiring. Other conditions will cause the door lock sensor to malfunction, including a broken “release wire bracket” found on the actuator.
Some brands of cars are more sturdy than others, and the fragile nature of door lock actuators varies across the different brands.
Some ways of fixing this problem include locating the entry point of water/moisture and sealing it off while covering the connectors in the actuator with protective grease. Confirm by pressing the door buttons on the key fob to ensure the door lock sensor is usually working. Also, observe for buzzing or humming sounds when the buttons on the key fob are pressed.
For a more straightforward and professional approach, use a scanner to continuously check for what has been triggering the alarm. It is always advisable to replace damaged parts with new ones.
5. Problem with your Key Fob
A key fob is a device (primarily plastic) that acts as a vehicle remote control. A key fob can either have a key embedded into the fob or without a key. Those fobs without a key are called keyless fobs and are usually found with keyless entry systems.
Usually, a radio transmitter is designed to be within the fob and sends a unique signal to the receiver built within the car. In perfect working condition, the critical fob increases the ease when the driver starts the car and opens or locks the car’s doors, all with a push of a button.
A faulty key fob will not correctly transmit signals to the car receiver, which can easily trigger the vehicle’s alarm system.
Batteries in the key fob can be drained after using the key fob for a long time, but such a challenge can be fixed with a simple replacement of the drained battery with a new one. From time to time, it is advisable to reset the key fobs. If your alarm keeps going off, faulty buttons or poor contact within the fob might occur.
However, if you do not notice any of the faults mentioned above and your car keeps going off, it will be wise to reconfigure the key fob with the help of professionals. If reconfiguration does not work, the professionals can use a scan tool to diagnose the key fob.
6. Your Hood Latch Wiring Might be Bad
Poor wiring is also a significant cause of malfunctioning in-car systems. Even after cleaning or replacing faulty sensors, if the wiring is not correct, the vehicle’s alarm could go off at any moment for no apparent reason.
To fix poor wiring in the hood latch, closely observe beneath the hood (bonnet) and watch out for disconnected or improperly connected wires. Poor wiring is not a common fault for alarm systems.
However, it must never be overlooked. Besides affecting the alarm system negatively, bad hood latch wiring can cause other defects, like switching on the warning light when nothing is wrong with the airbag.
Reconnecting the hood latch wiring properly usually rectifies the fault if there are no sights of physical damage. Some other things to look out for include damage to the latch, misalignment, rubber stop position, condition of the pull lever assembly, and cable binding or fraying.
In addition, check the hood’s lever and spring for anomalies. Visiting a professional for proper troubleshooting and repairs should not cost above $300
7. A Faulty Bonnet Latch Sensor
Sensors within the car systems are sensitive and can easily cause the vehicle’s alarm to sound. The alarm could be triggered for no apparent reason when sensors are faulty.
One such sensor is the bonnet latch sensor. The bonnet (hood) latch sensor is similar to a simple electronic switch that yells to you when the bonnet is open or closed.
Typically, a sensor in proper working condition would notice when the bonnet is not closed correctly and signal the driver through the warning lights on the dashboard. Still, a faulty sensor would not be able to detect appropriately when the bonnet is closed or has just been opened.
The inaccurate conclusions made by the bonnet latch sensor can trigger the car’s alarm at any point, irrespective of the time of day.
Different things can cause a faulty bonnet sensor, but dirt clog is usually the main reason. The sensor is located in the engine bay just above the headlights. Therefore, it could be covered with dirt and grease easily. Hence, it could malfunction and set off a false alarm.
The bonnet and its latch sensor could easily be cleaned with brake cleaner and a brush to prevent the alarm from going off.
If the alarm keeps getting triggered, the sensor must be replaced with a new one.
8. Sensor Connection Might be too Sensitive or Weak
The types of movement and shock sensors vary among vehicles. For instance, older vehicles usually contain two sensor types: a shock and a door sensor. Modern cars would have more. While modern sensor types may be changeable, the older ones usually have preset settings.
Similarly, having an aftermarket or brand-new alarm system affects sensor sensitivity. Volkswagen and Audi’s vehicles illustrate how a vehicle’s sensor sensitivity fluctuates since they are famous for having sensitive factory-made sensors.
No matter how many or sensitive the sensors are in a vehicle, their connection to one another is a solid fact. An alarm will undoubtedly sound if even one of the microphone, shock, door, proximity, tilt, or glass-break sensors is on.
Verifying that a tight electrical connection exists among all sensors is essential because the primary battery powers them. Take the vehicle to a nearby auto shop to inspect the alarm by a professional if one has no idea what to check.
Turning off Car Alarm: What to Do
Would you want to turn off your car alarm, here are methods that can be employed to put off your car alarm.
Turn on your vehicle
At times when your car alarm goes off, you can turn it off by inserting your key into the ignition and putting on in the vehicle
If your car’s alarm is still sounding after putting on the vehicle, you can try turning the key to the ACC( which supports low voltage features in the car, for example, radio) and wait patiently.
Lock or Unlock your Vehicle Doors
Another way in which you could switch off a car alarm is by pushing down the lock or unlock button on the key fob. If this doesn’t work, slot a physical key into the plastic controller beside the door handle and lock or open the car door.
Use the Alarm Shut-off Lever
Suppose you are using an aftermarket fitted alarm system. There is usually a lever that could shut off the car’s alarm. This lever is usually located just beside the driver’s seat. For more information on this feature, you could go through the instruction manual of the alarm system to confirm if it has this lever and where it is located.
If a professional auto technician installed the alarm system, then you could go back to the auto shop, and they will help find the lever
Removing the Alarm Fuse of the Vehicle
In rare cases where you have tried all the fixes and tricks aforementioned, and the alarm refuses to stop, the next option will be to remove the car’s alarm fuse from the fuse box.
However, before removing the fuse, ensure the battery terminals have been disconnected properly to avoid any electrocution incident. Note that this method might not work on modern models of cars as they have an integrated alarm system fixed into their ECU.
Remove The Car Alarm Wires
Anyone with technical knowledge of fixing car alarm systems could do this without contracting a professional. However, anyone who does not have an in-depth understanding of how alarm systems work should never try this. There are so many wires beneath the steering.
Resetting the Alarm System
One of the rare ways to turn off a car’s alarm is by resetting the vehicle alarm system. This method is ideal for vehicles that have independent alarm system modules. This method suits situations where the alarm gets triggered late at night. For more information, check the manual on how to reset the alarm system
Completely Removing the System
When every other option does not work, the best thing to do is to put off the whole alarm system, which can cause a nuisance at odd hours.
Shutting down the vehicle’s alarm system can be done in many ways; however, two methods stand out.
Method 1: You could remove the alarm system partially by disconnecting the alarm system totally from the car.
Method 2: The other way is by cutting the wires which connect the alarm system.
Total removal of the alarm system will destroy any chances of reconnection later, hence the wires’ cutting.
On the other hand, a partial disconnection can be reversed by reconnecting the unplugged connections. Recent models of cars I heavily computerized; therefore, to disconnect the vehicles alarm system, there might be a need to reprogram the ECU using a computer
Different methods can be used to shut off a vehicle’s alarm. These methods may require various tools, but the urgency to end the noise produced by the vehicle’s alarm will be the driving force needed to make you make swift decisions.
Car Alarm Goes off When Unlocking With Key: Solved
How can I solve the problem of my alarm going off randomly? There are so many methods to solve this problem. However, we will treat the answers to this question in classified categories to make the solution more understandable. Here are several factors that make your vehicle’s alarm system go off when using a key to open the car’s door.
1. Fixing Sensitive Sensors in the Vehicle
You are fixing damaged, or malfunctioning sensitive sensors is one way to get your alarm system in order. The best part is that you do not have to go all the way to a workshop to get it done. By browsing through the owner’s manual and following directions carefully, you can find these sensitive sensors and reconfigure or reset them.
The sensors can be reset to be less sensitive, reducing the probability of the car’s alarm going off at the slightest action. An example is opening the car door.
2. Repair of your Key Fob
A faulty key fob can cause your alarm system to malfunction; hence, repairing the critical fob can solve this issue. First, you can try fixing the battery. If there is no improvement, then the key for bleeds 22 is resetting.
3. Open your Vehicle with the Key Fob Instead of the Key.
If you find yourself in such a situation, you could easily use a remote key to open the car instead of using the metallic key. Whenever you are alarm is turned off mistakenly when opening your vehicle’s door. Immediately your car recognizes its key in the ignition; the alarm will turn off
4. Recharge your Car Battery if Necessary
A low battery voltage can cause your alarm to go off. Troubleshoot this problem with a voltmeter. Check the battery’s voltage; if it’s drained, you must charge it.
When the battery’s terminals are dirty, the battery can be cleaned with a cleaner. Wear personal protective equipment like hand gloves and goggles before handling the battery.
If the battery is too corroded and is beyond cleaning or repair, it is advisable to replace it. Once the battery issue is fixed, your car alarm shouldn’t go off again whenever you try to open it with a key
5. Fix the Malfunctioning Panic Button
Suppose you activate your panic button mistakingly and set your alarm off. You could quickly fix this by pressing your panic button again, stopping the alarm from sounding. If it refuses to stop, you could quickly turn off the car’s alarm by inserting your key into its ignition.
Other Reasons Why Your Car Alarm Can Go Off
1. A Working Shock Sensor
Motion is one thing that sets off alarms in cars; the shock sensor is the device that notices this motion. The Shock sensors detect motion through metal contacts touching one another upon bumping into a vehicle that activates the circuit.
Sophisticated shock sensors can even tell the degree of vibrations detected. This data are sent to the alarm system, which acts accordingly. When a person slightly bumps into a modern car with a complex alarm system, the alarm system might sound the car’s horn warning the person to steer off. This kind of sound will not be the same reaction the alarm system will give when someone uses a hammer to hit the car. The alarm will be loud and long with a touch of sirens in some types of vehicles.
Susceptible shock sensors can also detect loud sounds, like an explosion or a child screaming. Vibrations produced by the sound waves hit the car’s body, which may trigger the alarm to sound and disturb the whole block.
2. A Working Proximity Sensor
These sensors are not installed in your everyday alarm system. Proximity sensors are Usually found on high-end luxury cars. These sensors can detect objects and persons within a specified distance from the vehicle and send signals back to the alarm system.
3. A Working Tilt Sensor
Smart poachers may try to lift and tow your car away silently, which generally works, but adding tilt sensors to vehicles makes this very difficult.
The tilt sensors are built with a liquid metal called mercury. This metal is used to complete a circuit. If the car is lifted at an angle, the mercury will flow in the opposite direction, causing the course to become open.
Tilt sensors are probably the only defense from catalytic converter thieves. The car must be jacked at an angle to steal the catalytic converter. If this happens, the alarm will go off.
4. Sensors in the Hood Latch, Door, or Trunk of a Car
Many cars produced now have sensors, unlike when cars were made with fewer sensors and more mechanical calibration. However, hood latches, doors, and trunks are found in almost every alarm system. Sensors help to detect when any of these parts are unlocked.
These sensors are calibrated with spring-triggered buttons connected to the circuit, allowing power flow when the vehicle door is opened. This electricity flow is set off dome indicator, which in return sounds the alarm as conditioned by the ECU
5. A Working Microphone Sensor
Microphone sensors pick up sound from their surrounding. These sensors are configured to listen for unique sounds like glass shattering or thumping and send signals to the alarm system.
6. A Working Pressure Sensor
Including pressure sensors in a vehicle is another effective way to detect abnormalities and make the alarm go off. Usually, the air pressure in a car equals the air pressure outside the car. If the window breaks, the air pressure inside the vehicle will change, and if the pressure sensor inside the car detects this abnormally, the alarm will go off.
Although the pressure sensor is a stand-alone device, it is built into the sound system in some vehicles.
Speakers are very sensitive to vibrations, despite being able to produce sound waves. The sensitivity of the speaker can detect changes in air pressure.
When there is a rise in air pressure, the air becomes denser, and this slight change can cause vibrations detected by the speaker. The sensor on the speaker sends a signal to the alarm system.
Frequently Asked Questions – Car Alarm Goes off When Unlocking With Key
Will a car alarm drain the car’s battery?
Usually, factory-fitted alarm systems do not use up much power from the battery. Also, a well-installed aftermarket alarm system will not use up much power from the storm. Still, if the aftermarket alarm system is installed wrongly, it could run the battery down fast.
How can one deactivate a vehicle’s anti-theft system?
Slot the key into the ignition hole, then rotate it once to power the car accessories without igniting the engine. Keep the key in that position for about 15 mins. Then, take a look at the anti-theft warning light again. When it stops blinking, return the key to its first position and wait a few minutes.
How can one unlock a vehicle without beeping?
To unlock a car without beeping. Simply switch off the horn sound. This action can be done by holding the lock and unlock buttons simultaneously for some seconds. Wait till the danger lights flash three times. Then, lock the car doors and confirm that the car horn is deactivated.
Will a car alarm stop after unlocking the doors?
Many car alarms will be triggered after the car doors have been opened using its crucial fob or the proper keys. When door locks do not respond, it could mean that the remote vital batteries are drained.
What can cause a car alarm to start sounding?
Usually, alarm systems can be triggered by shock sensors or vibration sensors. They detect when the car is experiencing slight motion around it, including an unsuspecting dog or even a thief.
Can low battery power trigger a vehicle alarm?
A car’s battery always signals to the ECU whenever its stored power is used to start the engine. Therefore, if the battery is drained or low, the car’s engine will not start, but the signal will still be sent to the vehicle’s ECU. The alarm system will react abnormally to inform the driver that the battery needs replacement. A voltmeter can be used to check the battery’s voltage level.
Why will a car alarm refuse to go off?
Many things can cause the car alarm not to sound when it is meant to alert the driver of impending danger. Some reasons why the notice may not go off include a damaged key fob, faulty sensors, low voltage in the battery, or connection issues. The door not being properly locked can also cause this problem. Resetting the ECU might fix these problems. But if it doesn’t, then contact a professional.
How can one know if a car’s anti-theft mode has been engaged?
Modern cars possess a warning light indicating that the vehicle is in anti-theft mode. The anti-theft system symbol has a car and a lock sign. This symbol is always seen on the dashboard when the anti-theft mode is activated.
Is there any need to reprogram a key fob after changing the battery?
It is an unnecessary endeavor to reconfigure a key fob after battery replacement. However, if multiple components of the key fob were tampered with, reprogramming should be considered to avoid malfunctioning the critical fob after assembly. The remote key can be reprogrammed by inserting it into the car’s ignition hole again.
Conclusion – Car Alarm Goes off When Unlocking With Key
Alarms systems are a popular concept regarding security, and their incorporation with car systems helps protect the car from thieves and criminals. However, the alarm system might become a nuisance if it goes off when attempting to unlock the car, which can be disorienting.
The great thing about this problem is that it is temporary and has numerous solutions. In this article, we surfed the length and breadth of this problem, explaining in detail the causes and solutions to this problem.
In addition, we helped enlighten you on how to prevent this problem from occurring again and stepped in to improve your car’s alarm system. In conclusion, if you ever experience alarm problems and lack technical knowledge, visiting an auto repair shop and getting professional help is always wiser.