Car Alarm Keeps Going Off? Reasons Why & How To Fix

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Picture of By <span>Aren Mirzaian</span>
By Aren Mirzaian

Updated on August 17, 2023

Visit author page
Picture of By <span>Aren Mirzaian</span>
By Aren Mirzaian

Updated August 17, 2023

Visit author page

7 minute read

Article Contents
Car Alarm Keeps Going Off

A car alarm is a must for protecting your vehicle from theft and damage, but if it keeps going off for no reason, it can quickly become a stressful and annoying problem. 

An alarm that keeps going off can disturb your sleep and your neighbours, putting you at risk of being written up for a statutory nuisance notice. Worse still, false alarms can make you complacent, leaving you unprepared when your car is actually damaged or broken into. 

Learn some potential reasons why your car alarm keeps going off, how this could affect your car insurance, and how you can fix it or turn it off.

Top 10 Reasons Why My Car Alarm Keeps Going Off

In some cases, you can easily trace what’s causing your car alarm to go off constantly. Finding out what’s causing it will help you figure out how to fix a car alarm that keeps going off. Check first for these common causes:

1. Defective Door Lock Sensor

A door lock sensor has both an open circuit and a closed circuit installed inside its actuator, the mechanism responsible for locking or unlocking your doors. Here’s how to check if your door lock sensor is the problem:

  1.  Inspect your door lock connector and actuator in case they need to be replaced. Some cars have actuators with brackets that are prone to breaking.
  2. Check for water leaks caused by heavy rain, flooding, or other sources of water. If water leaks into your door lock sensor’s actuator connection, finding the source of the leak and sealing your connector with protective grease can keep your car alarm from going off.
  3. If a leak isn’t responsible, check the internal wiring with a scan tool. This can determine which door lock is responsible for triggering your car alarm.

2. Key Fob Malfunction

A key fob is a transmitter for keyless car entry. If it’s working properly, your key fob will lock or unlock your doors seamlessly, as well as jumpstart your ignition. 

In contrast, a dead or defective key fob will fail to send a signal properly to your car’s receiver unit. This can cause your car alarm to go off.

Here’s how to check your key fob for issues:

  1. Check if your key fob’s batteries are dead. After long periods of regular use, your key fob batteries will die, and replacement will quickly fix this problem.
  2. Remember that key fobs also need to be occasionally reset. If the battery is still working, try resetting the key fob.
  3. If the battery is fine and resetting doesn’t resolve this issue, you may need to disassemble your key fob and check if there are connection problems. In some cases, broken or rusty contacts or misaligned buttons are behind a defective key fob.
  4. If the buttons and contacts are fine, you may need to have your key fob scanned and reprogrammed by a professional.

3. Dirty Hood Latch Sensor

Your hood latch sensor detects when your hood is closed or open. When it functions properly, this sensor will light up your dash with a warning light and turn off the electrical switch. But if there’s too much dirt and grease collecting on the sensor, it can malfunction and set off your alarm.

Use brake cleaner and a brush to remove debris, dirt, and grease from your hood latch sensor. If cleaning doesn’t fix it and you suspect the hood latch sensor is damaged, replace it immediately.

4. Defective Hood Latch Sensor

In some cases, your hood latch sensor may keep going off even if you’ve cleaned or replaced it. Here’s what you can do if you think the hood latch sensor is faulty:

  1. Try disconnecting and reconnecting your car’s hood latch sensor. In some cases, this will make your hood latch sensor work properly again.
  2. If this doesn’t fix the problem, you’ll need to inspect your hood latch connection. Look for signs of wear, misalignment, or cable fraying. You can also check if the levers are bent or worn out.
  3. If you’re uncertain what signs to look for, bring your vehicle to a professional to check your hood latch sensor’s connections and repair them.

5. Poor Alarm System Installation

Factory alarm systems offer limited levels of security, so many car owners opt for post-market security options to protect their cars from thieves and intruders. 

Unfortunately, many post-market systems are improperly installed, especially when done in a home garage without the right tools. The constant screaming of a car alarm going off is a tell-tale sign that an aftermarket system was improperly installed. 

If you installed the system yourself, double-check the manual to make sure you followed the instructions. If you had it professionally installed, bring it back to your mechanic or shop and explain the problem. Reinstalling the system may fix the problem.

6. Low Car Battery

If your car battery is dead and your car alarm keeps going off, there may be something wrong with your car battery power. 

Many car owners may not know this, but low power can trigger car alarms. Get your voltmeter and check your car battery’s running voltage. If you get a reading below 12.6V or a reading below your car owner’s manual, your dead battery will need jolting or replacement.

7. Wiring Issues

If your key fob, car battery, or car sensors aren’t making your car alarm go off, your wiring may be the problem. Part of your car’s wiring may be disconnected or defective. If you suspect that faulty wiring is the cause, check for accompanying issues like constantly flashing headlights or a triggered car horn.

8. Sensor Connection Issues

Checking for sensor issues will depend on whether you have a newer or older car. Here are some key differences that can indicate which sensor connection issues to look for:

  • Newer cars have several sensors, while older vehicles will typically only have a door sensor and shock sensor.
  • Newer cars have adjustable settings, while older sensors have fixed factory settings for their sensitivity and functions.
  • You need to check if your car is using the factory alarm system or an aftermarket one. If your aftermarket one is improperly installed, this may cause your alarms to go off.

No matter how sensitive your car sensors are or how many there are in the system, they’re still connected to each other. All your car sensors will get power from your car battery, so check if there’s a continuous, regular power connection between all your sensors and the battery. 

If you’re not sure what signs to look for, take your car to your trusted mechanic or shop.

9. Control Module Problems

One of the considerations you should have when buying a new or used car is the complexity of its electronic control units (ECUs). The ECUs of newer cars are increasingly more complicated and designed to handle increasingly more information and functions.

If your car’s ECU has issues, this can send the wrong signals to various car parts and make your car’s safety system think your security has been compromised – setting off your alarm. You can’t fix your ECU on your own, so take it to a specialist for reprogramming if you think it’s defective.

10. Rusty Battery Terminals

When you have corroded battery terminals, the rust that forms prevents your car battery from giving enough power to your car. Your car alarm system may mistake this for low-power battery conditions, setting off your alarm as a warning.

Salt, excess moisture, and improper charging can cause rusty terminals. If the rusting is minor, you can remove the rust with a wire brush and a commercial-grade cleaning agent. But if the rusting is severe, consider replacing the whole battery.

Car Alarm Keeps Going Off

How to Turn Off or Disconnect a Car Alarm That Keeps Going Off

Here’s how to disconnect a car alarm that keeps going off, or how to simply turn it off until you can try the solutions we’ve listed above:

  • Unlock or lock your vehicle’s doors: In some cases, remotely locking or unlocking the doors with your key fob will stop the alarm. You can also use your physical key to do this and turn off the alarm.
  • Turn on your car: If your car lets you turn the ignition on even when the alarm is triggered, do so to turn off the alarm and spare the neighbourhood from continuous wailing. You can also try turning your car key to the ACC position (car radio on, engine not running) to see if this turns the alarm off.
  • Press the shut-off switch, if available: Some aftermarket security systems will have a concealed switch around the driver’s feet area. This switch can disable the car alarm, so check your system’s manual to see if it has one. 
  • Reset the alarm system: Most car security systems have their own control units for the alarms. If your alarm keeps going off, check the system’s manual to reset it properly and see if this fixes the problem.
  • Take out the alarm fuse: If checking on the doors and the key fob doesn’t fix the problem, removing the right fuse can keep your car alarm from going off. Note that this solution is more viable for older cars, as newer vehicle alarms are integrated into the car’s central module. Make sure the battery terminals are detached before you touch the fuses to avoid being electrocuted.
  • Remove your entire car alarm system: If nothing else has been able to turn off your car alarm, deactivating the system will do the trick. You can do this by snipping the wires for partial removal or removing the system wiring for complete removal.

What Do I Do if My Neighbour’s Car Alarm Keeps Going Off?

If your neighbour’s car alarm keeps going off, there are three things you can do. These are:

  • Call the police: If you suspect that the alarm is going off because someone is breaking into your neighbour’s car, call 999 right away.
  • Inform your neighbour about the repeated noise: If you suspect that your neighbour’s car alarm may be defective, tell them that it’s disturbing you and potentially other neighbours in the vicinity.
  • File a report with your local council: Talked to your neighbour, but still suffering through sleepless nights of noise? Report the nuisance to your local council’s Environmental Health team, and they’ll handle the issue.
Car Alarm Keeps Going Off

The Bottom Line

Some cars are more prone to theft than others, and having a car alarm protects your car from intruders. However, it can be a nuisance both to you and your neighbours if it isn’t working properly. 

Try checking for the common causes we’ve listed above, as well as their common fixes. In many instances, this problem can be resolved even without professional help.

A high-quality car alarm can lower your car insurance premiums. You can also lower your premiums by shopping around or changing car insurance mid-policy. Get car insurance quotes from trusted insurers using MyChoice – we can help you find the best match for your needs and budget.

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