The development of the automotive world is inseparable from innovations made from cars found until now, the large number of new car production has resulted in many old cars being abandoned. The engineering that has been carried out by the FIAT 124 S, the Toyota 5K Swap engine, has resulted in a problem with the body's electricity and the charging system, with the body's electrical engineering being carried out. The purpose of body electrical engineering is that the electrical and charging systems can work again. The body's electrical engineering process identifies body cable networks, continuity checks, electrical component checks, completes electrical components, after checking, assembling body cables and charging, connecting cables with components, loads, fuses, controllers, wrapping with cable protectors. From the results of the electrical engineering body current flowing in the circuit is calculated with a battery voltage of 12.5 V, low beam head lights (5.12 A), high beam (5.26 A), turn signal lights (1.05 A), city lights (0.52 A), wipers (2,87 A), horn (1.84 A), brake lights (2.02 A), charging system (13.04 A / 14.5 V), all systems work properly.