# Fake car alarm: does it put thieves off?

_Updated: 8 November 2026_

**Short answer:** A fake car alarm is a light that blinks like a real alarm. It may put off a thief looking for easy pickings, but a thief who checks the car soon sees there is no alarm: the light does not sound, does not alert you and does not stop the engine from starting.

> **The service we recommend: Car alarms** An alarm with a siren, and more expensive models add an app and GPS. We tell you the price when you tell us the model. [More about the service](https://autoindustrija.rs/en/services/car-alarm-installation)

## A fake alarm is a light with no sensors and no siren

The light has no sensors and no siren, so it does not know whether someone opened a door or broke a window. It blinks blue or red, like the light of a real alarm on the dashboard.

There is also a light with no wires that charges from a small solar panel. The light sometimes comes with a sticker saying the car is alarmed.

## Who a fake alarm puts off, and who not

A thief picks the car that looks easiest. In a British study, 100 car thieves talked about how they choose a car. Many said they recognise an alarm by a red light blinking on the dashboard. Fewer look for a sticker on the window. A thief like that may move on to another car because of the light.

Some thieves know that a light sometimes blinks without an alarm. So before a theft many of them kick a tyre or do something similar to see whether the alarm goes off. A fake alarm stays silent, and the thief knows the car has no alarm.

A fake alarm stays silent when a thief kicks a tyre to test the car.

A thief who comes prepared brings a device. Through the OBD port, where diagnostics are plugged in, they make a new key. If you have a keyless key, which unlocks and starts the car while it is in your pocket, the thief relays the key signal to the car and unlocks it. To them the light means nothing.

## Fake or real alarm

|  | Fake alarm | Real alarm |
| --- | --- | --- |
| Puts off a thief looking for easy pickings | Until the thief checks the car | Often, even when the thief checks the car |
| Sounds when someone opens a door, hits or moves the car | No | Yes |
| Alerts your phone | No | An alarm with an app |
| The engine will not start without your fob | No | An alarm with an engine lock |

## A real alarm puts thieves off even when they check it

In the same study, an alarm would put off up to 6 in 10 thieves. Many said they would rather take a car without an alarm, because it is less hassle. When the alarm goes off, some of them leave and look for another car.

A real alarm watches the doors, boot, bonnet and ignition, and its sensors feel a knock and the car being moved.

A thief can ignore an alarm that only sounds, but cannot drive away a car that will not start. That is why you should take an engine lock with the alarm. When you switch on the ignition, the alarm looks for a small fob that you carry with you, and if it is not in the car, the engine will not start.

## How a thief switches off an alarm, and how we prevent it

Thieves who switched off an alarm most often crawled under the front of the car and pulled out the wires of the siren or the battery. Others opened the bonnet and pulled the wires out.

That is why we fit the siren under the bonnet, where it cannot be reached from under the car. We hide the control unit, the box that runs the alarm, behind the dashboard. A siren with its own battery keeps sounding even when a thief cuts the cable or removes the car battery.

Almost half of the thieves also said that people take no notice of an alarm going off. That is why an alarm with an app alerts you. When the alarm goes off, you get a message or a call, and in the app you see the state of the car. [More about a car alarm with GPS](https://autoindustrija.rs/en/advice/car-alarm-with-gps)

## Which alarm to take instead of a fake one

You choose the alarm by where the car is parked and what you want from the alarm.

- **The car is parked outside your house or in the yard:** At least an alarm with a siren, because you hear the siren from the house.
- **You want to know what is happening even when far away:** An alarm that alerts your phone.
- **A more expensive car stays on the street:** An alarm with GPS and an engine lock. You see where the car is, and the engine will not start without your fob.
- **Your car has a keyless key:** An alarm with an engine lock and a fob. The engine will not start without the fob, even when a thief unlocks the car with the signal of your key.
- **The car is older and has no remote locking:** An alarm with its own remote. You arm and disarm the alarm with it.

[More about choosing an alarm](https://autoindustrija.rs/en/advice/best-car-alarm)

## What an alarm does not stop on its own

- **A thief makes a new key through the OBD port:** The factory alarm is switched off with the key. A thief who makes a new key through the OBD port unlocks the car like the owner, so the alarm stays silent. An alarm with a lock that asks for your fob makes the job harder for the thief. OBD port relocation closes that way of theft. [More about OBD port relocation](https://autoindustrija.rs/en/obd-port-relocation)
- **A thief unlocks a keyless car with the signal of your key:** An alarm that only sounds helps little here. An engine lock with a fob, an immobiliser, with which the engine will not start without your fob, and a pouch that blocks the key signal help. [More about the immobiliser](https://autoindustrija.rs/en/services/immobiliser)

## When a fake alarm makes sense

- Until you fit a real alarm.
- Next to an engine lock or an immobiliser, as a sign to a passing thief that the car is protected.

## Frequently asked questions

### Does a fake alarm drain the car battery?

A solar light does not drain the car battery, because it is not connected to the car. It charges from its own small panel.

### Do cars have a blinking light from the factory?

Some do, as part of the factory immobiliser or alarm. On a Mazda, for example, the light on the dashboard blinks every 2 seconds while the system is armed. Then a fake alarm only adds one more light.

### Does a real alarm drain the car battery?

A little. A healthy battery copes with that for weeks. A weak battery feels it if the car stands for a long time.

### Does comprehensive insurance give a discount for a fake alarm?

A fake alarm has no sensors and no siren, so it does not guard the car. Some insurers give a discount on comprehensive insurance if the car has an additional anti-theft device. When you tell the insurer the car has a real alarm, they tell you how much it lowers the price of the policy.

Have a question about your car? Message us on WhatsApp or call 067 774 1606.

## Read also

- [Car theft in Serbia: 9 ways thieves steal a car](https://autoindustrija.rs/en/advice/how-cars-are-stolen-in-serbia)
- [OBD car theft: how thieves make a new key](https://autoindustrija.rs/en/advice/obd-car-theft)
- [Keyless theft (relay attack): how it works, how to stop it](https://autoindustrija.rs/en/advice/keyless-car-theft)

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