how to turn it off

Hi, there,

I bought a Nissan Maxima three month ago. I didn't know it has after-market alarm. But it went out today. I tried to disconnecte the battery. But it went off whenever I connected the battery. I'm totally blind of the alarm. I don't know where the button to turn it off. What can I do? help!

What went of, the car horn or a separate siren?

 If it is a separate siren, you have an aftermarket alarm. There should be some kind of switch under the dash in the driver side. If you do not see it, you will have to disconnect the alarm. Look under the hood first to see if anything connected to the battery. If you see a fuse you can disconnect to see if this is the main power for your alarm. If not, you will have to go under the driverside dashboard and hunt for the brain of the alarm.

What out though, some alarms systems when you disconnect the brain from the alarm, you won't be able to start the car because the starter disable circuit will be open .

Jeff is correct. Let us know what's going on boywing. If you do have to go under the dash to look for the brain, you can may see the name.