What Causes a Car Alarm to Keep Sounding?

[McLevi]

There are several reasons why a car alarm may keep sounding, including an overly sensitive alarm or a faulty switch. Overly Sensitive Alarm: If the alarm is overly sensitive, even minor disturbances around the car, such as slight movements, can trigger it to keep sounding. This issue can usually be resolved by adjusting the sensitivity. The sensitivity of the anti-theft sensor may be set too high. To fix this, locate the sensitivity adjustment knob on the vibration sensor of the alarm system and make slight adjustments. Faulty Switch: A malfunctioning door contact switch can also cause the alarm to sound continuously. In this case, it is necessary to visit a repair shop for servicing. How the Alarm Works: When the sensor is struck or shaken, causing it to vibrate, a small ball inside the chamber rolls. As it rolls away from a smaller secondary electrical contact, the circuit formed by this secondary contact and the central electrical contact is broken.

[MacPaisley]

I've been repairing cars for twenty years, and I encounter alarm malfunctions several times a day. The most common issue is the vibration sensor acting up—it can get triggered by a passing truck on the road, let alone mischievous kids slapping the car for fun. Checking whether the doors and trunk are properly closed is crucial, as an unlatched door is the second most frequent cause of trouble. Poor wiring connections often cause problems too, especially in modified cars where short circuits are more likely, and corroded alarm control unit connectors are quite common. My advice is to first try using the remote to unlock the car and see if that turns it off. If that doesn’t work, disconnect the negative battery terminal for three minutes to reset the system. If it still keeps blaring, just remove the panel under the steering wheel and pull the alarm fuse—that’ll definitely shut it up.

[CalvinLynn]

Last week, my car kept triggering false alarms in the neighborhood, and the property management almost issued a fine. A friend suggested I walk around the car first, and I found the left rear door was slightly ajar. Sometimes, when parked under a tree, strong winds can cause branches to hit the hood and trigger the alarm. Nowadays, many cars come with radar sensors, and even something like gum stuck on the door handle can cause false alarms. Another common issue is the remote control getting stuck in the seat gap and pressing the buttons accidentally. Troubleshooting is simple: press the unlock button three times to see the response, then check each door to ensure it's properly closed. If you're sure it's not a false trigger, it's likely a fault in the alarm system's computer board, and replacing the entire system may be necessary for a permanent fix.

[LeCharlotte]

My Tiguan had the same issue. The alarm went off at 2 AM, causing complaints from neighbors. The 4S shop suggested checking the key battery first, as a coin battery below 3 volts can send erratic signals. The sensor micro-switch near the trunk latch is most prone to dust accumulation—cleaning it with a toothbrush can solve the problem. Another hidden issue is the sunroof; water leakage that flows to the center console can trigger the anti-intrusion alarm. I recommend keeping a small notebook to log the alarm timing patterns. If it consistently goes off exactly 10 minutes after locking the car, it’s likely a false alarm caused by leakage in the ultrasonic sensor wiring.

[Dawson]

After the heavy rain two days ago, my Buick started giving erratic alarm signals. The mechanic said rainwater seeping into the wheel arch's speed sensor connector can cause this, essentially making the system misjudge the vehicle as stolen. Older cars require extra attention to check if the door hinge wiring harness has worn through the insulation. Once when I removed the door panel, I found the power window motor wires had their copper strands sliced by the window frame. If you're handy, you can disconnect the battery and perform your own tests: use a multimeter to measure the voltage at the alarm module's power terminal—it should read 12 volts normally; if the resistance at the grounding terminal exceeds 1 ohm, you'll need to sand off any rust. However, if there's an issue with the electrochromic rearview mirror wiring, you'll have to rely on professional diagnostic equipment.