That the battery in your car is low and needs to be charged
no it doesn't if the door is opened when its ON it makes a circuit and starts the car alarm
If you set the alarm (i.e. lock the car) and then disconnect the battery, the alarm will go off. If you disconnect the battery when the alarm is not set (i.e. when the car is unlocked) the alarm will not go off. (So don't try to nick a locked one).
Disarm the alarm before removing the battery.
sounds like the battery short-circuited.
unplug the car battery this should reset the system. If it doesnt, i presume you do not have the remote for it? I assume the doors are locked also? put the key in the door turn it left, right, left. this should de-activate the system. If there is a kill switch, also known as a valet switch it should be under the dash on the drivers side near where the fuse panel is.
Car alarms normally work on the battery that starts the car.
Insert the ignition key into the ignition and turn it to on, the alarm should shut off.
no you cannot kill your alternator by switching your battery from one car to another
take them out . you should charge battery then be ok.
Car alarm in Lexus ES300 started going off at random when car was parked, not running. I changed the key fob battery (flat watch battery) with a new battery and it fixed the problem.
You can get a car alarm that uses it's own battery so wont drain the car.