14.2. Detection of not closed chain
The usual electric chain consists of an electric element, switches, the relay, engines, safety locks, automatic switches, wires and sockets which connect an electric element to the accumulator and a body.
Before to try to define a malfunction source, study the corresponding scheme of electric equipment for receiving idea of the elements established in this chain. The circle of possible sources of malfunction can be narrowed if to check functioning of other elements entering this chain. If several elements or chains vykholit out of operation at the same time, then the problem, obviously, consists in a safety lock, the general for these chains / elements, or contact with a body.
Electric problems are usually caused by the simple reasons: the weakened or rusted sockets, lack of contact with a body, the fused safety locks, the melted burned-through crossing point or the faulty relay. Visually check a condition of all safety locks, wires and sockets in the failed chain before to start check of other elements. Use schemes of electric equipment for definition of what of trailer clips need to be checked for detection of a source of malfunction.
The main tools necessary for detection of a source of malfunction, the tester or the voltmeter are (the bulb on 12 volts and couple of wires with probes on the ends can be also used for conducting some checks); ohmmeter; the battery and a set of wires with probes, a cap puncture, it is desirable with the automatic switch or a safety lock which is used for a round of the checked wires or elements.
For detection of the reason of unreliable work any of elements (usually because of bad connection / pollution of contacts or the damaged isolation) it is possible to carry out an inspection stirring of wires. It is necessary to shake a wire by a hand to check whether malfunction at the movement of a wire appears. By such method it is possible to narrow a circle of possible sources of malfunction to any wire.
Along with problems because of bad connection of wires two main types of malfunctions can take place in system of electric equipment – the opened chain or short circuit.
Problems with the opened chain appear as a result of break in electric equipment chain that interrupts course of current. The opened chain will cause shutdown of an element of electric equipment.
Problems with short circuit are caused by short circuit of the site of a chain that leads to leakage of current from other chain, usually directly on a body. Short circuit is usually caused by a rupture of isolation of wires that allows a wire to concern other wire or any grounded element, for example, of a body. Short circuit usually leads to burn-out of the corresponding safety lock.
Detection of a rupture of a chain
The majority of problems of the opened chain are caused by the broken or weakened socket.
Detection of a source of short circuit
Elements of loading of a chain are elements which consume electric current, such as bulbs, electric motors, heating elements, etc.
Detection of bad grounding
The negative plug of the accumulator is connected to "weight" – metal of a body, the engine or transmission. At the same time many elements of electric equipment are connected in such a way that only the positive wire approaches them, at the same time current comes back to the accumulator through body metal. It means that fastening of an element of electric equipment and a body are a part of an electric chain. Therefore the bad or rusted fastening can cause failure in the functioning of an element or lead to its unstable or bad work. In particular, bulbs can burn with dim light (especially if in a point of grounding of this bulb grounding any else the switched-on electric equipment element is carried out), electric motors can slowly work, and also work of one chain can have effect imperceptible at first sight on work of other chain. Do not forget that on many cars grounding wires between some elements, such as engine / transmission and a body are used, that is in those places where there is no direct contact between metal elements because of soft rubber fastenings or a paint coat.