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 current to the rechargeable 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 this chain. If several elements or chains fail at the same time, perhaps, the safety lock, the general for these chains or elements is faulty, or connection with a body - "weight" is broken.
The weakened or oxidized sockets, violation of contact with a body, the fused safety locks or faulty relays are causes of defect. 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 trailer clips which need to be checked 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 V, an ohmmeter, the battery and a set of wires with probes are, it is desirable with the automatic switch or a safety lock which is used for a round of the checked wires or elements.
Except violation of connection of wires in system of electric equipment, 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 current is interrupted, 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 rechargeable battery or the grounded element, another – to contact in the checked chain, it is desirable for the next to the rechargeable battery or a safety lock. The checked site of a chain has to be energized from the rechargeable battery, except for a case when the socket of connection to the battery does not carry current or the safety lock fused (do not forget that some chains of electric equipment join only at turn of a key in the ignition lock in a certain situation).
Include a chain, then connect the tester probe to connection, the next to the chain switch on the party of the checked element.
If there is tension (what fire of a control lamp or the indication of the voltmeter testifies to), so on the site of a chain between the corresponding connection and the switch there are no gaps.
If the site on which there is no tension is found, so the break of a chain happened between this point and a point of the previous check on which there was tension. The 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 conclusions of a tester or the voltmeter to contacts of a safety lock.
Include food in chains; do not forget that some chains of electric equipment join only at turn of a key in the ignition lock in a certain situation.
If in a chain there is tension (what fire of a control lamp or the indication of the voltmeter testifies to), so in a chain short circuit.
If when checking there is no tension, and the safety lock still fuses at connection of the same loading, – the loading element failed.
The negative plug of the rechargeable battery is connected to "weight" – a body, the engine or the 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 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.
For check of reliability of grounding of an element it is necessary to switch-off the rechargeable battery and to connect one of ohmmeter conclusions to reliably grounded element. Connect other conclusion to a wire or connection with a body which needs to be checked. Resistance shown by an ohmmeter has to be equal to zero, otherwise check connection as it is described below.
If reliability of contact with "weight" raises doubts, investigate connection, remove pollution and smooth out contacts. At assembly tighten fastening of the socket for what put a layer of technical vaseline or silicone lubricant for prevention of corrosion.
An inspection of an integrity of a chain is carried out to be convinced that a chain, its site or an element carry current. Disconnect wires from plugs of the rechargeable battery and connect the probe of a control lamp with own power supply, for example the device for check of an integrity of chains, – to one end of a chain, and other probe by the second end of a chain. If the lamp lights up, so the chain is not interrupted and carries electric current. Switches can be checked in the same way.