Car alarms that go off for no reason may be triggered by low vibrations caused by a passing car or a small animal. They can also be triggered by loud noises and failing to close the door or trunk properly. A typical car alarm system consists of a controlling unit, sensors and an alarm; an electrical fault in any of these may cause the alarm to go off for no reason.
Car alarms come with different kinds of sensors that affect how they respond to activity around them. In addition to shock sensors, car alarm systems may also come with radar or motion sensors. These are designed to sense movement within the immediate outer perimeter of the car as well as inside. Car alarm systems also come with tilt sensors, which trigger the alarm if the car's position is moved. Other key components of a good car alarm system include glass break sensors and hood pin triggers. Knowing the type of sensors or upgrades included in your alarm system can help narrow the possible causes of the alarm.
Car alarms are also affected by voltage settings, so a persistent alarm may be an indication of a weakened car battery. To determine if a car alarm is being triggered by vibrations or activity, try parking it in a different zone.