all of my interior lights went out

[omar.b.saida]

in my 85 all of my intrument cluster lights went out along with my tail lights. all of the other lights work(blinker, brake) and i cant figure out if its a fuse or not because all of the fuses are still in good along with i have power to all the wires. and for the tail lights i replaced the bulbs but they still dont work. with the instrument cluster lights am i just going to need a whole new cluster or is there a way to replace the lights?

[bd]

Have you tried turning the dash lamp dimmer fully counterclockwise? 

Two battery sources feed the headlamp switch.  One is for the headlamps, the other is for all the other switch controlled lights. 

For the tail and dash lights, electrical power flow is from the 20-amp tail lamp fuse to the headlamp switch, where it splits "through the switch" to simultaneously run out to the tail lamps and up to the dash lamps.  The dash lamp circuit then runs through the dimmer rheostat back to the 5-amp instrument lamp fuse and up to the dash lamps.  So, the tail lamps are protected by the tail lamp fuse - the dash lamps are protected by the tail lamp fuse AND the instrument lamp fuse.  The tail lamp fuse should be hot all the time.  The instrument lamp fuse will be hot only after switching on the running lights.

The 168/194 dash bulbs plug into 1/4-twist sockets from the back of the instrument cluster and are individually serviceable by first removing the cluster from the dash.

Now, with all of that stated, you posted that you "have power to all the wires."  Does that include the orange wires connecting to the headlamp switch?  How about the brown and dark green wires?  Or, are you saying that you have power to the tail and dash lamp bulbs, but none of them work?  Do the forward park lights and side marker lights work?  Have you checked and/or serviced any of the ground connections? 

Grounds are a continuous source of grief on these trucks.  There are one or two grounds at the rear lamps, sheetmetal grounds under the dash, battery-to-engine, battery-to-frame, battery-to-radiator support, cab-to-engine, and engine-to-frame grounds.  All must be in perfect condition or you'll be plagued by mysterious electrical symptoms. 

Answer the questions I've posed and provide a little more information so the Forum can help you zero in on a solution.

In the meantime, see Diagnosing dash lights that don't work in our Technical Pages and refer to the 1985 Wiring Manual as necessary.