How to Install a Car Alarm

Whether you just bought a used vehicle without an alarm or just decided to opt for the extra security, installing an alarm system into your car is never a bad idea. There are a number of practical benefits, and in some areas, the addition of an alarm system can lower the cost of car insurance.

A car alarm is a fantastic defense against auto theft, and there are a number of alarms available that anyone can simply install in their own car. Though the process is not as simple as an oil change, the installation is surprisingly straightforward, if close attention is paid to the following directions, double-checking along the way.

Part 1 of 4: Pick out an aftermarket alarm

There are varying degrees of complexity available with car alarm systems. Basic systems can tell when a door is ajar or when an automatic lock is forced open. Complex systems have remotes that can warn you when your car is being tampered with and can detect when the car is bumped. Try to find an alarm that is designed for your vehicle to help the installation process.

Step 1: Search for a factory alarm. Check to see if there is a factory alarm system available for your specific model of car. Most manufacturers offer an alarm as an option, and in some cases, the installation of a factory unit can be incredibly straightforward. Some computer reprogramming may be needed by the dealer on some units to enable it.

  • Tip: You can usually get a key fob with a “panic” button on it from the manufacturer that matches the car’s regular key.

Step 2: Decide what you need from an alarm system. It is important that you have an idea of what you want from your alarm system and to search based on those preferences. If you just want a simple system, you can get set up with little cost to you. If you want a remote control that will alert you when your alarm is going off and the ability to start or stop your engine remotely, then you can spend much more on an advanced system.

  • Note: Your price range will be the biggest deciding factor here, so weigh out the pros and cons of installing an alarm system before deciding on the level of security you require. Very complex alarm systems may require professional installation.
car alarm installation
Image: Alibaba

Step 3: Read the Manual. Once you have an alarm system picked out, you need to read the manual for the alarm system and any relevant sections of the vehicle’s manual.

It is important to plan out the entire installation before diving into the project. An alarm that does not function correctly is not very useful and is potentially extremely annoying. Disconnect the battery before starting the installation. Be aware of any airbag wiring usually encased in yellow covers and connectors. Do not wire into any airbag circuit.

Part 2 of 4: Install the siren

Materials Needed

  • Electric tape
  • Handheld Drill
  • Multimeter
  • Mechanic gloves
  • Soldering Iron or Crimping Tool
  • Wire strippers/cutters
  • Zip ties

  • Note: When purchasing the alarm system, check the manual to see what additional tools may be required for installation.

alarm siren inside of engine bay

Step 1: Where to Mount. Find a metal surface onto which you can mount the siren that goes to the alarm system. The siren is the part that actually emits a high pitch sound, so it needs to be in the engine bay and it needs to be unobstructed. Try to keep the siren 18” away from hot engine components like the exhaust manifold or a turbocharger, facing the siren downward to prevent any water from entering the part.

firewall with holes for wiring

Step 2: Find a Hole for Wires. The wire needs to go through the firewall that separates the engine from the car’s interior. This means either finding a preexisting hole that wires are passing through already and using this space or drilling a hole into a plastic or rubber section of the firewall. This hole will also allow a power line to pass from the battery to the ‘brain’ of the alarm system, giving it power. It is a good idea to wire a fuse into this line.

  • Warning: Do not drill through the metal of the firewall unless it is absolutely necessary. You run the risk of damaging important components and causing premature corrosion.

Part 3 of 4: Wire the alarm into the car

alarm wiring within dashboard

Step 1: Find where the alarm computer connects. Using the manual that comes with the alarm, establish where the ‘brain’ of the system is going to reside.

Most need to be wired into the car’s ECU to read the signals pertaining to the sensors in the doors and windows. Some alarms have their own standalone computer units that are mounted in the engine bay near the siren, but most are wired into the car’s computer and hidden inside of the dashboard.

  • Note: Common locations include under the driver side of the dashboard and behind the glove compartment.

Step 2: Install additional sensors. If the alarm system came with any additional sensors, such as a shock sensor, then those can be installed now wherever the manufacturer suggests.

LED light switch

Step 3: Plan a place for LED lights. Most alarm systems come with some sort of indicator to tell the driver when the system is active. Usually, this indicator is in the form of a small LED light that is mounted in the dash somewhere, so plan out where the LED will fit best.

Step 4: Install LED lights. Once you have determined a fitting place, drill a small hole, and secure the light in place, wiring it to the rest of the system.

Part 4 of 4: Connect the battery and test the alarm

powerlines going to fuse

Step 1: Check the power. Connect the power line to the battery and allow the alarm system to power up. The system should power up when the car is on.

  • Warning: Some systems may need additional calibration at this point, so be sure to check the manual that comes with the system before continuing.

person trying to set of alarm with tool

Step 2: Check the system. Arm your system and then test it to see if it functions properly. If your system comes with a ‘panic button’ remote, test it using that, but your system does not have a remote, try jostling the door while the alarm is armed.

Step 3: Bundle loose wires. If the system is working properly, then you can use electrical tape, zip ties, and/or heat shrink wrap to bundle the loose wires together and protect the connections.

Step 4: Secure the wires. Since the wires are now bundled together, secure the brain and the wires somewhere inside the dashboard. This will prevent issues with the unit from getting jostled around, which may set off the alarm unnecessarily, causing unwelcome distress and concern.

Once the system is secured, your car is much less likely to be stolen thanks to the measures you have taken. Installing a car alarm is a painless way of ensuring that your car is protected from criminals, giving you the peace and comfort that comes from knowing your car is safe. Car alarms may seem daunting, especially to the beginner, but you need not let this keep you from installing an alarm and protecting yourself and your car.

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