1995 Silverado electrical problem

Hi, I have a electrical problem that is causeing many problems to do with the wipers, 4WD, heater blower, and gear indicator light. None of these things work when I try to use them. When I turn the ignition switch backwards to just play the radio I turned the wiper control switch and I hear a buzzing noise coming from the wiper motor also all the tach lights show up very dimm. I disconected the wiper motor and tryed to see if all the funtions worked again but no luck. I started noticing problems one day when the gear indicator light began flickering one day and eventually stayed on as the vehical warmed up and now it only appears when I turn the igniton switch halfway then disappears once the truck is fully started, and now nothing works.
any help would be greatly appreciated!
thanks.