14.2. Detection of not closed chain

THE GENERAL DATA

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The prevention

Before to begin work with any of elements of system of an electric equipment of the car, it is necessary to disconnect a wire from the negative plug of the accumulator for prevention of short circuit and / or ignitions at work.

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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 an electric equipment for representation reception about the elements established in this chain. The circle of possible sources of malfunction can be narrowed if to check up functioning of other elements entering into the given chain. If some elements or chains выхолят out of operation simultaneously the problem, obviously, consists in a safety lock, the general for these chains / of elements, or contact to a body.

Electric problems are usually caused by the simple reasons: the weakened or rusted sockets, absence of contact to a body, the fused safety locks, the fused burnt through crosspiece or the faulty relay. Visually check up a condition of all safety locks, wires and sockets in the failed chain before to start check of other elements. Use schemes of an electric equipment for that definition what of trailer clips are necessary for checking up for detection of a source of malfunction.

The basic tools necessary for detection of a source of malfunction, the tester or the voltmeter (a bulb on 12 volt and the pair of wires with щупами on the ends also can be used for carrying out of some checks) are; an ohmmeter; the battery and a set of wires with щупами, накидной a puncture, it is desirable with the automatic switch or a safety lock which is used for detour of checked wires or elements.

For detection of the reason of unreliable work any of elements (usually because of bad connection / of pollution of contacts or the damaged isolation) it is possible to inspect stirring of wires. It is necessary to shake a wire by a hand to check up, whether there is a malfunction at wire movement. 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 basic types of malfunctions can take place in electric equipment system – the opened chain or short circuit.

Problems with the opened chain appear as a result of breakage in an electric equipment chain that interrupts current course. The opened chain will cause switching-off of an element of an electric equipment.

Problems with short circuit are caused by short circuit of a site of a chain that leads to leak of a current from other chain, usually directly on a body. Short circuit is usually caused by rupture of isolation of wires that allows a wire to concern other wire or any earthed element, for example, bodies. Short circuit usually leads перегоранию a corresponding safety lock.

Detection of rupture of a chain

The majority of problems of the opened chain are caused by the broken or weakened socket.

PERFORMANCE ORDER

1. For check of integrity of a chain connect the device for check of schemes or negative щуп the voltmeter to the negative plug of the accumulator or the earthed element. 2. Connect the second щуп to connection in a checked chain, it is desirable for the nearest to the accumulator or a safety lock. Thus this site of a chain should be energised from the accumulator if only the connection socket to the accumulator does not spend a current or has not fused a safety lock (thus do not forget that some chains of an electric equipment join only at key turn in the ignition lock in certain position). 3. Include a chain, then connect щуп a tester to the connection nearest to the switch of a chain on the party of the checked element. 4. If pressure is present (about what the control bulb testifies or voltmeter indications), it means that the chain site between corresponding connection and the switch has no ruptures. 5. Continue chain check by the same image, site detection on which there is no pressure, means that chain rupture has occurred between this point and a point of the previous check on which there was a pressure.

Detection of a source of short circuit

Elements of loading of a chain are elements which consume an electric current, such as bulbs, electric motors, heating elements etc.

PERFORMANCE ORDER

1. For detection of a source of short circuit in the beginning disconnect elements of loading of a chain. 2. Remove a corresponding safety lock and connect щупы a tester or the voltmeter to safety lock plugs. 3. Include a food in chains, thus do not forget that some chains of an electric equipment join only at key turn in the ignition lock in certain position. 4. If pressure is present (about what the control bulb testifies or voltmeter indications), it means that in a chain there is a short circuit. 5. If at carrying out of check of pressure is not present, however the safety lock on the former fuses at connection of that loading of a chain, it testifies to failure of an element of loading.

Detection of bad grounding

The negative plug of the accumulator is connected to "weight" – to metal of a body, the engine or a transmission. Thus many elements of an electric equipment are connected in such a manner that the positive wire, thus a current approaches to them only comes back to the accumulator through body metal. It means that fastening of an element of an electric equipment and a body are a part of an electric chain. Therefore the bad or rusted fastening can cause refusal of work 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 it is carried out grounding of any else included element of an electric equipment), electric motors can slowly work, and also work of one chain can have an effect imperceptible at first sight on work of other chain. Do not forget that on many cars grounding wires between some elements, such as the engine / transmission and a body, that is in those places where there is no direct contact between metal elements because of soft rubber fastenings or a paint coat are used.

PERFORMANCE ORDER

1. For check of reliability of grounding of an element it is necessary to disconnect the accumulator and to connect one of щупов an ohmmeter to reliably earthed element. 2. Connect another щуп to a wire or connection with a body which is necessary for checking up. 3. Resistance shown by an ohmmeter should be equal to zero; if is not present, check up connection as follows. 4. If you assume absence of grounding, disassemble connection and clear a site of a body and the wire plug (or a surface of grounding of an element) to pure metal. 5. Carefully remove all traces of a dirt, then by means of a knife remove all paint so that reliable contact of two metal surfaces has turned out. 6. At assemblage reliably tighten socket fastening; at connection of the plug of a wire establish a washer with the jagged edges between the plug and a surface of a body for maintenance of reliable connection. 7. At connection prevent corrosion occurrence in the future, having put a layer of vaseline or silicone greasing.