hi i have a problem with my vectra i was driving it the other day without any problems starting and that same day i took it to s c motor factors to get parts for my other car, it started fine when i went down there. then came back out and went to start and it just clicks once and all the dash lights go off then back on. so i thought it could be battery so i put a jump pack on but nothing just the sameing. so i bump started it and it started fine but when you put lights on and steer all the dash light flicker and the head lights go dim then off and back on again when you stop steering it all seems fine. i got it home and turned it off and went to start it again and same thing just a click and all lights flickering then all come on and seems fine but wont start. and to top it all of when locking and unlocking to car some times it will unlock and lock it self and the alarm gos off then you hit the button to unlock stops the alarm but you carnt unlock the car lol

what dose people think my problem can be?