10.2. Diagnostics of malfunctions of electric equipment

The basic electric element, various switches, the relay, electric motors, safety locks, fusible inserts or breakers of a chain relating to this element, the conducting and contact sockets serving for connection of a basic element with the rechargeable battery and "mass" of a body can be a part of a typical electric chain.
Before getting to work on elimination of malfunctions in any electric chain, attentively study the corresponding scheme as much as possible to have a clear view of its functional purpose. The circle of troubleshooting is usually narrowed due to gradual definition and an exception of normally functioning elements of the same contour. At simultaneous failure of several elements or contours burn-out of the corresponding safety lock or violation of contact with "weight" is the most probable cause of refusal (different chains in many cases can become isolated on one safety lock or a conclusion of grounding).
Failures of electric equipment often are explained by the elementary reasons, such as corrosion of contacts of sockets, failure of a safety lock, burn-out of a fusible insert or damage of the relay. 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 units carefully plan (according to the 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 tester of electric chains or the voltmeter (it is possible to use also a 12-volt control lamp with a set of connecting wires), the indicator of break of a chain (sampler) including a lamp, own power supply and a set of connecting wires are among the main diagnostic units. Besides, for launch of the engine from a foreign source (the rechargeable battery of other car) it is always necessary to have a set of the wires equipped with clips like "crocodile" 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 diagnostics of a chain. As it was already mentioned before starting check of a chain by means of the diagnostic equipment, determine by schemes of the place of its connection.
Verifications 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 rechargeable battery or provide good contact with a car body. Connect other wire of a tester to contact of the socket of the checked chain, preferably to the next to the rechargeable battery or a safety lock. If the control lamp of a tester lights up, supply voltage on this piece of a chain is that confirms serviceability of a chain between this point of a chain and the rechargeable battery. Working in the same way, investigate other part of a chain. Detection of violation of supply voltage demonstrates existence of malfunction 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 the 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 has to be absent. Pull conducting, watching a lamp sampler. If the lamp begins to blink, somewhere in this plait of wires there is a short circuit on "weight", perhaps, caused by a mastication of isolation of wires. A similar inspection can be carried out for each of components of an electric chain by turning on of the corresponding switches.
Check of reliability of contact with "weight". Disconnect the rechargeable battery and connect to a point with obviously good contact "weighing" one from wires of the lamp sampler having the independent power supply. Connect other wire of a lamp to the checked plait of wires or contact of the socket. If the lamp lights up, contact with "weight" as it should be (and vice versa).
An inspection on lack of break is carried out for detection of breaks of an electric chain. After power off of a contour check it by means of a lamp sampler with the independent power supply. Connect sampler wires to both ends of a chain. If the control lamp lights up, there is no break in a chain. If the lamp does not light up, then it demonstrates existence in a break chain. Similarly it is possible to check also serviceability of the switch, having connected a sampler to its contacts. At transfer of the switch to the provision of "VKL" the lamp of a sampler has to light up.
Localization of the place of break. At diagnostics of the suspect available of break of the site of an electric chain visually to find a cause of defect it appears to check quite difficult as happens hard visually plugs for 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 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 on condition of a clear idea of the fact that electric current arrives to all consumers (a lamp, an electric motor and so forth) from the rechargeable 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 failure of electric equipment can be caused by interruption in supply on them electric current from the battery or return of current to the battery.