Jacob's brake problem

I have a cat c12, and my Jacob's brake worked before I had my heat and air worked on behind the dash, my wiring has 3 wires blue, yellow and green in loom from brake switch, through the firewall to motor, none have power to.them with test light, relay is in fuse box but nothing to attach it to on back side of box, and no wires connecting to my clutch switch, any help.would be appreciated thanks

 

2002 Ford sterling it used to have the Mercedes motor in it swapped it out for the cat c12 motor, if not mistaken the Jake switch has 4 prongs and only 3 wires are hooked to it , green, yellow and blue, wonder if that 4 prong was a hot qire for switch