This machine was worked on for a hub seal leak. The cab was tilted to replace the brakes booster assembly. There was also a jump wire install to put in a horn button. The power was pulled from a brake relay power wire. The machine has power at the dash, the shift lever activates the backup alarm; but when the key is turned to the start position there is no response it will not start. We tested and all other functions seem to be sending signal except for the start signal. We tested the ignition switch and we have a signal there for start. It seems like a bad relay or broken wire. We cannot locate the wire for ignition going through the harness. Any schematics or knowledge of the issue.