10.2. Diagnostics of malfunctions of electric equipment
The structure of a typical electric chain can include the basic electric element, various switches, the relay, electromotors, safety locks, fusible inserts or the breakers of a chain relating to this element, conducting and the contact sockets serving for connection of a basic element with the storage battery and "mass" of a body.
Before starting to work on elimination of malfunctions in any electric chain, attentively study the corresponding scheme as much as possible to be clear in the mind about its functional purpose. The circle of troubleshooting is usually narrowed at the expense of gradual definition and an exception of normally functioning elements of the same contour. At simultaneous failure of several elements or contours the most probable cause of refusal is the peregoraniye of the corresponding safety lock or violation of contact to "weight" (different chains in many cases can become isolated on one safety lock or a grounding conclusion).
Electric equipment refusals often speak the elementary reasons, such as corrosion of contacts of sockets, safety lock failure, a peregoraniye of a fusible insert or relay damage. Visually check a condition of all safety locks, conducting and contact sockets of a chain before starting more detailed check of serviceability of its components.
In case of application for troubleshooting of diagnostic devices carefully plan (according to enclosed electric circuits), in what points of a contour and in what sequence it is necessary to connect the device for the most effective detection of malfunction.
The number of the main diagnostic devices includes a tester of electric chains or the voltmeter (it is possible to use and a 12-volt control lamp with a set of connecting wires), the break indicator the chains (sampler), including a lamp, own power supply and a set of connecting wires. Besides, for engine start-up from an extraneous source (the storage battery of other car) always it is necessary to have a set of the wires equipped with clips of the crocodile type in the car and it is desirable the breaker of an electric chain. They can be applied to shunting and connection of various elements of electric equipment at chain diagnostics. As it was already mentioned before starting chain check by means of the diagnostic equipment, determine by schemes of a place of its connection.
Stock-takings of supply voltage are carried out in case of violation of an electric chain. Connect one of wires of a tester of electric chains to the negative plug of the storage battery or provide good contact to a car body. Other wire of a tester connect to contact of the socket of the checked chain, preferably to the next to the storage battery or a safety lock. If the control lamp of a tester lights up, the supply voltage on this piece of a chain is that confirms serviceability of a chain between this point of a chain and the storage battery. Operating in the same way, investigate other part of a chain. Detection of violation of supply voltage testifies to malfunction existence between this point of a chain and the last from checked earlier (where there was a supply voltage). In most cases the cause of failure consists in weakening of contact sockets and damage of contacts (oxidation).
Searches of a place of short circuit. One of methods of search of short circuit is extraction of a safety lock and connection instead of it of a lamp sampler or the voltmeter. Tension in a chain should be absent. Pull conducting, watching a lamp sampler. If the lamp starts to blink, somewhere in this plait of wires there is a short circuit on "weight", probably, caused by a peretiraniye of isolation of wires. Similar check can be carried out for each of components of an electric chain by turning on of the corresponding switches.
Check of reliability of contact to "weight". Disconnect the storage battery and connect to a point with obviously good contact to "weight" one of wires of the lamp sampler having the independent power supply. Other wire of a lamp connect to a checked plait of wires or socket contact. If the lamp lights up, contact to "weight" as it should be (and on the contrary).
Check on absence of break is carried out for detection of breaks of an electric chain. After shutdown of a food of a contour check it by means of a lamp sampler with the independent power supply. Connect sampler wires by both ends of a chain. If the control lamp lights up, break in a chain is not present. If the lamp does not light up, it testifies to existence in a break chain. Similarly it is possible to check and serviceability of the switch, having connected a sampler to its contacts. At transfer of the switch to the situation "VKL" the lamp of a sampler should light up.
Localization of a place of break. At diagnostics of the suspect available break of a site of an electric chain visually to find a cause of defect it appears to check quite difficult as happens hard visually plugs on emergence of corrosion or violation of quality of their contacts because of limited access to them (usually plugs are closed by the case of the contact socket). Sharp twitching of the case of a block of a plait of wires on the sensor or the plait of wires in many cases leads to contact restoration. Do not forget about it in attempts of localization of a cause of failure of the chain suspected available of break. Unstably arising refusals can be a consequence of oxidation of plugs or violations of quality of contacts.
Diagnostics of malfunctions of electric chains does not represent a difficult task under condition of a clear idea of that the electric current arrives to all consumers (a lamp, the electromotor and so forth) from the storage battery on wires via switches, the relay, safety locks, fusible inserts, and then comes back to the battery through "mass" (body) of the car. Any problems connected with refusal of electric equipment, can be caused by interruption of supply on them an electric current from the battery or return of a current to the battery.