98 Passat Alarm

The battery on the car died. It was replaced and the car would run for 5 seconds and die. We took it to the dealer. They reset the computer and now it works. The stereo was locked out which we fixed. Now the alarm is being wierd. It opens and closes the locks fine, however the horn isn't beeping like it used to. Do you have any suggestions on why the horn will not beep. I know is some cars the horn is adjustable but there is no info in the owners manual about how to do this.