If you have checked all the obvious places like windshield & wiper shaft rubbers, here is the real doozie that caused my leak: The air intake grill (between the hood and the windshield), for the heater has a drain built into the internal structural channel. This drains down through the internal channel behind the fuses, and then out the little hole in the rocker guard. You can find it by removing the inside panel and looking with a flashlight while running a hose into the grill. My car had apparently had an accident before I bought it and some of the internal bracinfg was bent so that the water splashed down onto the car, instead of following Volvo's intended path to the drain. Good luck.