13.24.3. 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. For the help by search of sources of malfunction of system of electric equipment in section 14 schemes of electric equipment of the car are provided.
Before trying 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 fail at the same time, then the problem, obviously, consists in a safety lock, the general for these chains or elements, or contact with a body.
Electric problems are usually caused by the simple reasons, such as 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 starting 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 in system of electric equipment – the opened chain or short circuit can take place.
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.