1989 325i electrical problems, please help

hey, i just purchased a 1989 325i and its got a few problems. pretty much its an intermitent power problem. sometimes the windows, turn signals, gas guage, tach and temp dont work. and sometimes they do. the previous owner replaced the IS board which as i understand is a common problem. any help would be greatly appreciated. im thinking it may be a bad ground or a bad connection somewhere under the dash but this is my first BMW and i have limited knowledge on them. thanks in advance...Nick

anyone?