7.1.1. Definition of a source of malfunction
The electric chain consists of an electric element, switches, the relay, electric motors, safety locks, automatic switches, wires and sockets which connect the consumer of a current to the storage battery and a body. For the help in search of sources of malfunction of system of electric equipment in the management 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 elements of this chain. The number of possible sources of malfunction can be reduced if to check work of other elements entering into this chain. If some elements or chains fail at the same time, possibly, the safety lock, the general for these chains or elements is faulty, or connection with a body – "weight" is broken.
Causes of defect are the weakened or oxidized sockets, violation of contact to a body, the fused safety locks or faulty relays. Visually check a condition of all safety locks, wires and sockets in the failed chain before starting check of other elements.
Use electric equipment schemes for definition of trailer clips which are necessary for checking for definition of a source of malfunction.
The main devices necessary for detection of a source of malfunction, the tester or the voltmeter, a control lamp on 12 are In, an ohmmeter, the battery and a set of wires with щупами, it is desirable with the automatic switch or a safety lock which is used for round of checked wires or elements.
Except violation of connection of wires in electric equipment system, two more main types of malfunctions – separation of a chain or short circuit are possible.
The chain is disconnected because of break, as a result the current interrupts, causing shutdown of an element of electric equipment.
For definition of an integrity of a chain connect the device for verification of schemes or the voltmeter: one conclusion – to the negative plug of the storage battery or the earthed element, another – to contact in a checked chain, it is desirable for the next to the storage battery or a safety lock. The checked site of a chain should be energized from the storage battery, except for a case when the connection socket to the battery does not carry out a current or fused a safety lock (do not forget that some chains of electric equipment join only at key turn in the ignition lock in a certain situation).
Include the chain, then connect щуп a tester to the connection closest to the switch of a chain on the party of the checked element.
If there is a tension (to what fire of a control lamp or the voltmeter indication testifies), means, on a chain site between the corresponding connection and the switch there are no gaps.
If the site on which there is no tension is found, means, break of a chain occurred between this point and a point of the previous check on which there was a tension. Break of a chain is caused by the damaged or weakened socket.
For detection of a source of short circuit switch off consumers of the electric power – lamps, electric motors, heating elements, etc.
Remove the corresponding safety lock and connect tester or voltmeter conclusions to safety lock contacts.
Include a food in chains; do not forget that some chains of electric equipment join only at key turn in the ignition lock in a certain situation.
If in a chain there is a tension (to what fire of a control lamp or the voltmeter indication testifies), means, in a chain short circuit.
If at check of tension is not present, and the safety lock still fuses at connection of the same loading, – out of operation there was a loading element.
The negative plug of the storage battery is connected to "weight" – to a body, the engine or a transmission. The unreliable or oxidized fastening can lead to refusal of an element or violation of its work. Do not forget that on many cars "mass" wires between some elements, such as 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.
For check of reliability of grounding of an element it is necessary to disconnect the storage battery and to connect one of ohmmeter conclusions to reliably earthed element. Connect other conclusion to a wire or connection with a body which is necessary for checking. Resistance shown by an ohmmeter should be equal to zero, otherwise check connection how it is described below.
If raises doubts reliability of contact to "weight", disassemble connection, remove pollution and smooth out contacts. At assembly tighten socket fastening for what put a layer of technical vaseline or silicone greasing for corrosion prevention.
Check of an integrity of a chain is carried out to be convinced that the chain, its site or an element carry out a current. Disconnect wires from plugs of the storage battery and connect щуп a control lamp with own power supply, for example the device for check of an integrity of chains, – by one end of a chain, and another щуп by the second end of a chain. If the lamp lights up, means, the chain does not interrupt and carries out an electric current. Switches can be checked in the same way.