I have a 99 blazer with 4.3 vortec (140,000 miles).About one month ago, auto headlights would not come on and everything in the dash went crazy intermitly. Radio would not work, door locks, tach speedo etc.etc. etc. Changed headlight switch in dash and problem went away for awhile. Now speedo, tach, radio and door locks will not work and the last time everything worked 4 wheel was engaged and that will not work either so its stuck in 4 wheel. Need help bad!!!!!!