The Vectra B is an estate vehicle produced by Vauxhall between 1995 and 2002. Over time, the powersounder batteries in the alarm can become worn out and cause the alarm to sound even when the sensors have not been triggered. If left untreated, this will cause the alarm wiring to short out.
Place the key in the door lock of your Vectra. Open up the driver's door and enter the driver's seat.
Locate the alarm wiring control panel below the steering wheel column. Pry the cover off the panel with a flat head screwdriver.
Put on a pair of protective gloves. Pull the alarm wiring away from the electrical connectors with your hands.
Remove the bolts attached to the alarm module with a socket wrench. Lift the module away from the dash. Place the panel back over the wiring control.