The majority of car alarms use a horn or other audio warning device to alert passersby that the door has been opened. In many cases, the alarm is only designed to sound if the battery is disconnected as a deterrent against theft. If you happen to disconnect your own car’s battery enough so it won’t start, but still have enough power to set off your alarm – usually by jumping – what happens?
2 Reasons why car alarm goes off when jump-start a battery
Here are two reasons why a car alarm goes off when you jump-start a dead battery:
1. It’s a failsafe
Many modern cars have a “failsafe” mechanism that can activate an alarm if an attempt is made to break into or hotwire the vehicle without first entering the proper security code. The intent of these systems is to discourage thieves before they even enter the car, but what are the results when friendly folks like you disconnect your own car battery?
Many alarm systems will detect an open wire or switched circuit as a possible “entry” attempt. If there’s enough juice for this to happen, it’ll also activate the horn which should scare away any would-be intruders until you can get reconnected and turn off the system manually.
2. Faulty wiring
If your alarm has no failsafe mechanism, then faulty wiring could be setting it off unexpectedly. This can happen if your security system doesn’t have jumper cables plugged in all the way, or if you’ve accidentally crossed one of them too far installation or repair work underneath the hood.
Faced with a dead battery and an activated alarm, what do you do? Don’t panic! Modern alarms like the one in your car will deactivate themselves after about 15 minutes if no further intrusion occurs. All you have to do is reset it from your car’s interface or by disconnecting the cables from the terminals long enough for them to lose power.
One last thing: In some cases, a very weak battery can still trigger a false alarm due to a faulty connection with the vehicle’s electrical system. It may be possible that your battery appears fine on paper but has trouble transferring energy through its damaged cell walls. Replacing it with a new one could solve both problems at once.
Frequently Asked Questions
How do I stop my car alarm from going off when I jump it?
The easiest way to stop it from going off would be to disconnect any of those two systems by either removing wires or repairing them with wire clamps. If this doesn’t solve your issue, make sure nothing like a steel ratchet or creeper sets off the alarm and try using an insect repellent such as Hot Shot near enough for animals to smell and sense its presence.
Why is my car alarm going off when I change the battery?
For major corrosion on the battery (+/-) terminals that will not rub away with just wrist action, try using a towel or tissue to clean up any flakes and spit/urinate drippings from your system area – this saltwater solution might help loosen up the minerals sufficiently enough for further cleaning. Be careful though not to get too much moisture onto connections or wires which could cause them concern during use.
