Ford Repair: F150 electrical, electrical instrument, loose wires

Question
instrument lights not working at same time running lights are out. fuses checked good.However found 2 wires diconnected from each other on electrical brake box i installed 2 years ago for trailer. touched them together but nothing came on, only noticed it when i depressed brake pedal and light blue wire sparked when touched to metal

Answer
can you say test light-i take it your working on early 90s truck because if you are working on later model you will knock out an electronics module one of these days arcing wires. have it checked out.
have the two loose wires soldered so they won't come loose again-check connection on headlamp switch make sure not burnt between two terminals.
pull knob out slow and see if at some point dash lights flicker before it is pulled all the way out. good luck.