2002 crew cab eletrical problems

during daytime all lights work, except when stepping on brake pedal radio lights go dim,thermometer and compass also go dim. with directional lights radio goes dim with each blink. When headlights come on tach and speedo. do not work. Alternater and oil pressure gauges work. Also left rear blinker only works during daytime. With headlights on left rear blinker stays on [like brake light stuck on]. I checked battery ground, body ground,. State police already pulled me over for taillight . need your help........ thanks

check all fuses, in the cab and outside of the cab, check all wires all the way back

during daytime all lights work, except when stepping on brake pedal radio lights go dim,thermometer and compass also go dim. with directional lights radio goes dim with each blink. When headlights come on tach and speedo. do not work. Alternater and oil pressure gauges work. Also left rear blinker only works during daytime. With headlights on left rear blinker stays on [like brake light stuck on]. I checked battery ground, body ground,. State police already pulled me over for taillight . need your help........ thanks

Take a voltmeter and test the battery voltage when the truck is running.