Ford Ranger electric problem

My son’s 1998 Ford ranger will at times have no dome light or power window and often will not have windsheild wiper power when this happens. I have listened when this occurs and it sounds like a switch or relay under the passenger dash is turning off when there is no power and then will click on and all is restored. The domelight sometimes will click off seconds after opening the driver’s door and then the car has no windows or dome light. How do I trace the module or relay that is problematic??