The owner’s manual for your vehicle should include a section on the exact battery replacement interval you should expect. It’s a good idea to change the batteries once every year or two just in case. Since the key fob sends commands to the car’s computer relating to the alarm system, a fob with issues can send false alarm signals.įirst, try replacing the battery in the key fob if you haven’t done so recently. Reasons Your Alarm Is Going OffĪ car alarm that goes off randomly with no rapscallions around can have another underlying issue. They can detect when someone is too close to the car and give a pre-recorded verbal warning. These are really only used in very advanced systems, like in expensive vehicles. These listen to sounds and have been programmed to only notice and signal for breaking glass. Therefore, in reverse the sound waves move the speaker and the wires send a signal. Speakers make sound by moving back and forth to vibrate the air, creating sound waves. Sometimes the sensors are a separate device, but in some cars the built-in speakers can actually be used to “hear” the pressure change. Pressure sensors detect this small change in pressure and signal the computer. Pressure SensorsĮven if the ambient air pressure inside and outside the vehicle are the same, breaking a window briefly increases the pressure inside the cabin. Tilt sensors detect when the car is tipped by using mercury as the conductive metal liquid to close the circuit.Ī car alarm with a tilt sensor is often the only type that may prevent catalytic converter theft (if the thief actually jacks up the vehicle). More advanced alarms, however, have found a way to deal with this. Some thieves are more clever and will simply tow the vehicle away to avoid triggering the alarm system. Sometimes very loud noises can set off the shock sensors, because of the sound waves pummeling the vehicle. Sometimes a sensitive or basic alarm is set off by a cat jumping up onto the hood, which will probably wake up the entire neighborhood. It’s very helpful to have a system that can tell the difference between big and little bumps. Sometimes this means that if a passerby bumps into the vehicle they’re given a little honk of the horn and loud wailing if they hit the car with a crowbar. More advanced systems can determine the severity of the bump as well, leading the computer to respond appropriately. Shock sensors detect movement of the car by using metal contacts that touch one another when the car is sufficiently bumped to complete the circuit. Related: 5 Reasons Your Car Door Won’t Shut Shock Sensors This power illuminates the dome light and sets off the alarm, if the computer deems this necessary. These sensors use a spring-activated button or lever to close the circuit (which lets the power flow) when the door opens. Newer cars have more sensors than older cars, though most alarm systems have at least door, trunk, and hood latch sensors to tell when these are opened. See Also: Brake Lights Won’t Turn Off? (Here’s Why) What Can Trigger a Car Alarm? The security system sometimes has a backup power source in case a potential thief cuts the battery cables to try to make a quiet getaway.īasic alarms sense a big drop in voltage, like if a door is opened, an attached trailer with an electronic connection to the car is detached, etc. The receiver “hears” commands from a remote key fob via radio signals and responds by directing the vehicle’s battery-powered loudspeaker to emit the alarm sound when needed. 7) Incorrectly Installed Alarm System or Faulty Alarm ModuleĪlthough there are many possible vehicle security systems, the basic design is the same.Ī computer (sometimes the car’s ECU, sometimes a separate module for the alarm system) receives input from sensors throughout the car and from the receiver.5) Dirty or Malfunctioning Door Lock or Trunk Sensor.3) Corroded, Rusty, or Dirty Battery Terminals.
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