14.2. Detection of malfunctions
Read about safety measures (section 14 see) before the work beginning.
Following tests are intended for check of the basic electric chains and they should not be used for check of sensitive electric chains (such as system ABS), especially in the event that in a chain is the electronic operating block.
The typical electric chain consists of an element of an electric equipment, switches, the relay, engines, the safety locks, burnt through crosspieces or automatic switches and wires and connections which connect all elements among themselves and connect them to the accumulator and (weight) of the car. To simplify troubleshooting process, in subsection 14.20 electric schemes of system of an electric equipment of the car are resulted.
Before the beginning of check of a faulty chain, in the beginning study the basic scheme of this chain to understand from what elements it consists.
The malfunction source can be found faster if to define, what of elements of this chain work normally.
If some elements or chains fail at once, the problem, possibly, consists in the fused safety lock or bad grounding as frequently one safety lock is responsible for some chains.
Problems with work of system of an electric equipment are usually caused by the simple reasons, such as the oxidised or unreliable contacts, the fused safety lock, the fused burnt through crosspiece or the faulty relay (the description of operation of check of the relay see in subsection 14.3).
Visually check up a condition of all safety locks, wires and connections in a faulty chain before the beginning of check of other elements of this chain.
If you are going to use instrumentations, use basic schemes to define, what connections are necessary for checking up for failure detection.
The basic devices necessary for search of malfunction in a chain of an electric equipment, are the voltmeter (or a bulb on 12 Volt with connecting wires), the device for check of integrity of chains, an ohmmeter (for resistance measurement), the accumulator with connecting wires and накидным a wire, it is desirable with the automatic switch which can be used for parallel connection to a chain.
Before the beginning of search of malfunction with use of the control and measuring equipment, study basic schemes to define connection points.
For search of unreliable connection or a short circuit point (usually because of the bad either polluted connection, or the damaged isolation) it is possible to shake wires by a hand to see, whether there is a chain out of operation at wire movement. Such way it is possible to find a point with unreliable connection or a point in which there is a short circuit. This method of check can be used along with other tests described in following subsections.
Besides the problems connected with bad connection, the electric chain can have two other basic malfunctions – rupture presence in a chain or short circuit.
Rupture in a chain can be caused rupture of any wire or absence of connection somewhere in a chain that will prevent a current current. Rupture in a chain will cause refusal of any element of an electric equipment in work, but will not lead перегоранию a safety lock of this chain.
The malfunctions connected with short circuit, are caused by short circuit somewhere in a chain that leads to that the current flowing on a chain, starts to flow on other chain, and more often, leaves on (weight). Short circuit is usually caused by isolation rupture that allows a feeding wire to concern either other wire, or the earthed element, such, as a body. Short circuit leads перегоранию a safety lock of a corresponding chain.