1995 Chevrolet Suburban

I have a 95 suburban I was driving home from work an then it just lost all power no lights, raido, or anything it was like someone took the power from it so I waited for the next day went out to start the truck an it fired up but the minute I went to put it in drive it shut down like before I had the battery tested its good the starter tested its good I just don't know if I wiggle the key in the ignition the power comes back but as soon as I go to start my truck it like someone takes the power away please help me someone
January 2, 2013.

Check your battery connections. Was the battery and charging system tested on the vehicle? This testing needs to done on the vehicle. Maybe a problem with some of the wiring circuits? Check for voltage at your fuse box/fuses, Some fuses are hot all the time, some go hot with the key on, check for voltage, both ways. Yes, your ignition switch could be causing your problems. Any testing has to be done when the problem is ongoing.

Jan 2, 2013.