To visually find not closed chain happens rather difficult as it is often difficult to notice the oxidized or bad connection of contacts. It is sometimes rather simple to move a wire of connection or a wire in a plait of wires to eliminate this malfunction. Unreliable work of elements of electric equipment is also often caused by the oxidized or bad connection.

Finding of malfunction in system of electric equipment is represented rather simple operation if to understand that work of system of electric equipment is based that current flows from the accumulator through wires, switches, the relay, safety locks and the burned-through crossing points to electric equipment elements (a bulb, the engine, etc.) and on the mass of the car from where it comes back to the accumulator. Any malfunction in system of electric equipment represents a hindrance during current from or to the accumulator.