The negative plug of the accumulator is connected to "weight" — to metal massive unpainted parts of a body, the engine or a transmission. Thus many elements of electric equipment are connected in such a manner that only the positive wire approaches to them, and the current thus comes back to a battery battery room through a body. It means that fastening of an element of electric equipment and a body are a part of an electric chain. Thereof the bad or rusted fastening can cause refusal of work of an element or lead to its unstable work. In particular, bulbs can burn with dim light (especially if in a point of grounding of this bulb it is carried out grounding of any else included element of electric equipment), electric motors can slowly work, and work of one chain can have impact imperceptible at first sight on work another. Do not forget that on many cars grounding wires between some elements such, as engines/transmissions and a body, that is in those places where direct contact between metal elements because of soft rubber fastenings or a paint coat is absent are used.

For check of reliability of grounding of an element it is necessary to disconnect the storage battery and to connect one of щупов an ohmmeter to reliably earthed element. Connect another щуп to a wire or connection with a body which is necessary for checking. Resistance shown by an ohmmeter should be equal to zero — if is not present, check connection as follows. Clear a site of a body and the wire plug (or a surface of grounding of an element) to pure metal. Carefully remove all traces of dirt, then by means of a knife remove all paint so that reliable contact of two metal surfaces turned out. At assembly reliably tighten socket fastening. At connection of the plug of a wire establish a washer with the jagged edges between the plug and a body surface for ensuring reliable connection. At connection prevent emergence of corrosion in the future, having put on this site a layer of vaseline or silicone greasing.