94 gmc pick up pops brake fuse right away changed brake light switch and blinkers and tail lights still work y no 4ways or brake lights??

Could be the brake lamp switch is bad , stop lamp fuse 20 amp in under hood fuse box could be blown .Check the fuse ,if not blown check for B+ voltage at the brake switch , location - top of brake pedal under the dash . Do you know how to test automotive electrical circuit's using a DVOM - digital volt ohm meter ? Looking at a wiring diagram so you know which wires to test would be good too . Do you know what a wiring diagram is ? Free ones here http://www.bbbind.com/free-tsb Enter vehicle info. Year , make , model an engine size . Under system click on lighting ,then under subsystem click exterior lighting . Click the search button then the blue link. first diagram top left you will see the stop lamp switch . orange wire in is B+ voltage . Press the brake pedal while checking for B+ coming out on the white wire . No B+ coming out ,replace the switch . Will be other wires as well , other switch etc... check the right one .
Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts
Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia

First, verify that the brake lights work correctly with the old lights. If your blinkers work, the brake lights should work as well.
It is possible that your brake lights were not working previously. If they do not work, suspect a blown fuse or a defective brake light switch.

I have to believe that with all of the "non related" issues happening that there is a wiring harness problem. If you track the harness back from the tail lights you will probably find a nick or a break in the line. If nothing shows then check the connection point which should be somewhere around your fuel tank. It will be a male/female fitting that will pull apart and you can check at that point with a meter if it is working to that point. If not it then you will have to work your way all the way up to find the fault point.

check earth wires for light circuits and dash

fuse

most like u have a blown fuse most of the time in cars they connect the tail light and instrament lights to 1 fuse

I have notice that this is a common problem. The socket most of the time goes bad, I don't know why but they just do. You can pick them up at any parts store for around 5.00 each. If you don't have a volt meter and ground straps to test it right, then I would try changing the sockets out. Quick and easy. Let us know how it goes.

brake lights and turn signals work off the same curcit, it could be the fuse or the brake light switch !!!!!!

Check for power out of brake light switch by brake pedal. Of its faulty , the 3rd brake light will still work. Hope this helps

exactly what does it do? please explain what happens when you press the brake turn on the light than brake signals ect.....