1990 celica gts

My 1990 celica gts has developed a short which drains the battery when it is turned off. I have had problems with the passenger window(we think it's the switch), the sunroof (opens only after it has warmed up), and the passenger tail light(it has burned out more than any other light on the car), but my mechanic still has been unable to locate the short. Does anyone have any ideas?
Thanks---jean