Installing an alarm in a VW Beetle requires considerable knowledge of car electrical systems, especially on the classic Beetles of the past. Older VW Beetles have likely had multiple electronic add-ons installed over the years or even complete rewiring of the car itself. Make sure you have a wiring diagram no matter which model Beetle the alarm is going in.
Read the alarm manual carefully and ensure you fully understand the wiring diagram. Open the hood on a newer Beetle or lift the backseat on an older model. Remove the positive battery cable from the terminal and connect the alarm power wire.
Mount the alarm siren under the hood, facing the engine in a later model Beetle. Run the wires through the firewall and pull them into the cabin, under the dash. Run a classic Beetle's power wire under the carpet of the passenger seat and into the dash.
Secure the shock sensor as instructed in the alarm manual. If the vehicle has power locks, locate the lock relay and attach the alarm lock module.
Locate the starter wire in the ignition harness behind the steering wheel and connect the start disable relay. Drill a small hole in the dash for the LED light or use the existing light on newer models.
Connect all of the wires to the alarm control module and secure the module as far into the dash as possible with zip ties. Classic models have a great deal of room behind the radio for a more secure installation.
Reconnect the positive battery cable on the VW Beetle and test the alarm. Adjust the alarms sensitivity and secure any loose wires with zip ties.
Weaving the alarm wires into existing wire bundles makes them more difficult for a thief to identify, but be careful with old wiring as the cover may be brittle and flake away.