Car won't start after alarm went off.?

Need more information; what car is it? What happened? Does the car have a locking system? If you have a newer or higher end car then they have a security anti-theft system that disables the car temporarily to prevent theft. The way to get ur car to start back up is by a remote signal from the car dealer you bought it from, or from a special tool............. Or there could be a missing security chip which is ussualy under the steering wheel.......... But I highly suspect that the alarm went on for so long that your battery ran out. The alarm takes alot of battery, you should have it jump started and it should work..=)

The year, make, and model of your vehicle matters. For a mid 90s GM, the answer would be to reset the security system by using the key to lock and then unlock the driver door. I suspect something similar is your problem.

John: On some vehicles, disconnecting the battery will actually CAUSE the symptoms you claim it will fix.

Short is killing the battery have alarm checked and have alternator tested and battery tested at your auto parts store free of charge, if none of the last two then check alarm wiring.

if all else fails disconnect the batt for 10 mins then re connect it. imobiliser will reset along with ecu. please check if your stereo has a security code, if it has find the code to avoid getting pi**ed off