Car Alarm Goes Off

6 Causes Why Your Car Alarm Keeps Going Off

In Electric by 10 Comments

The car alarm buzzing for no reason is a common issue reported by many people.

The problem gets even more frustrating at night when people are sleeping, and suddenly your car alarm goes off without any apparent reason.

Why does this happen? Luckily the alarm is not getting off every time because of a thief; sometimes, a faulty installation or other reasons also cause the alarm to go off.

The most common causes why your car alarm keeps going off are low battery voltage, faulty hood latch sensor, a faulty door lock actuator, or a faulty programmed shock sensor.

Here is a more detailed list of the 6 most common reasons why your car alarm keeps going off.

1. Low Battery Charge

Car Battery Charger

A bad car battery or low battery charge is a widespread problem for a car alarm that goes off during the night. If you hear the car alarm going off at night and the car battery is dead in the morning, the car battery may be bad.

If your car battery is going off, but you can still start your car without any problems, it is most likely something else faulty, though.

You can test your car battery with a car battery tester, to see how good it is and replace it if it is bad.

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2. Sensitive Shock/Movement Sensor

Car Alarm System

A sensitive shock or movement sensor tends to trigger the alarm even if a dog or a cat gently touches your car. The type of shock sensors and movement sensors you have in your car depends a lot on your car model and if the car alarm is an aftermarket alarm system installed in your car or a car alarm from the factory.

In some car models with a car alarm from the factory, you can program the sensitiveness of the shock and movement sensors with a diagnostic scanner.

This is often needed on cars like Audi and Volkswagen because their sensors are over-sensitive from the factory and will go off sometimes.

Some aftermarket car alarm systems do also have adjustable sensors. Check the car alarm manual for more information.

3. Faulty Hood Latch Sensor

Latch Sensor Location

Modern vehicles are equipped with a hood latch sensor, which triggers the alarm if someone is trying to force open your car’s hood.

Depending on your car’s condition, it is very likely that dust, grime, and debris will collect where the hood latch sensor is located, and this causes the alarm to go off.

To fix this problem, locate the sensor and have it cleaned. If you can still hear the alarm sound, it is possible that someone tried to tamper with the sensor or the sensor is damaged. Replace the sensor if you think it may be faulty.

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You can find the hood latch sensor inside the hood lock most of the time, but it can also be installed externally.

4. Faulty Door Lock Sensor

Door Lock Sensor

The same as with the hood latch sensor, your car alarm monitors your car doors to make sure no one is opening your door.

Therefore a faulty door latch sensor can cause the car alarm to go off. The door latch sensor is often installed inside the door lock actuator but can sometimes be installed externally from the lock.

To find the faulty door latch sensor can be quite tricky if it just happens sometimes, though.

A door latch sensor usually has two wires to it, which are open circuit when the door is open or closed circuit when the door is closed or vice versa. This makes it pretty easy to measure with a multimeter.

The door actuators are often located inside the door, though, so it might be a little bit difficult to measure if you do not measure from the control unit instead.

5. Faulty Key Fob

Key Transponder

The key fob, also known as a car remote key, is a device that is used to lock/unlock your car doors and even start the engine with just a push of a button.

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Since the key fob also has controls linked with the car alarm system, a malfunctioning or faulty key fob can send an incorrect signal, which may trigger the car’s alarm.

You can check and replace the essential key fob batteries or reset the device to fix the problem. When you have replaced the batteries, and you have communication problems, you may have to reprogram your key fobs in some situations.

6. Incorrect Installation of the Alarm

Car Installation Alarm

If you have recently installed a new car alarm system and noticed that the alarm keeps going off for no reason, it may be because of incorrect installation.

In case you let a mechanic workshop install it, go back and explain your problem, and if you installed it by yourself, it is time to recheck the installation manual and double-check everything.

7. Bad Alarm Control Module

Alarm Control Units

Car alarms installed from the factory often have an integrated alarm control unit and a main electric component control unit, so a faulty control module is not common.

An aftermarket car alarm often has an alarm control module that controls all sensors and switches; if this control module fails, it may cause the car alarm to go off now and then.

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10 thoughts on “ 6 Causes Why Your Car Alarm Keeps Going Off ”

  1. My Audi 08 alarm keeps going off for a few seconds, No indicators flashing at all, it also did this today while driving?? Help Please.

  2. Thank you Magnum, I found your article very useful. I will give it a try.

  3. Hi, the hazard lights keep going off when the ignition is on, driving or still, engine on or off they just randomly go off. It’s not the hazard light switch because that works fine and it’s a flash with no indicator noise like when you lock or unlock the doors not like when you have the indicators on or hazards on and it makes a tic tok noise, there is no sound, it’s like the car is thinking the doors are being locked and unlocked when there not. They can flash for 2 secs of 2 mins, it is totally random. The fuses are fine the battery is fine and hhd key fob is fine, tried resetting the immobiliser a couple if times but nothing stood them flashing randomly. It’d a 2005 citroen c4. Tjankd

  4. I just experienced this problem and after 4 times going out to check it in the middle of the night, a big moth flew into my face and then out the door.. so far no more alarms. Apparently the moth was setting off the motion sensor inside the vehicle.

  5. My theft dash light blinking it cranks over but won’t start can u help

  6. I have a ford focus 62 plate….my car alarm keeps going of for some unknown reason also when I’m driving its says on dashboard that my bonnet is open but irs not ive cleaned sensors etc replaced car battery but still the problem is there driving me me Loonie

  7. Audi a4 2003 keeps flashing like hazards and it shows “safe” on dash board and it doesn’t start what do I do please!!!

  8. I Had the same problem, I replaced the locks, and the coils for the spark plugs, the muffler system
    was rotted replaced, the part that solved the problem was the CONVERTER car boned up changed it
    solved make sure your engine is running Right. Clean

  9. My 2012 Volvo S60 alarm has been going off intermittently since I had the 75,000 mile service done a few weeks ago. Dealer can’t replicate and wants $1,000 to replace sensors and “see if that fixes it.”
    Shade whaddayathink?

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