7.1. The general data
Cars Audi have system of an electric equipment with working pressure 12 V.Elektrooborudovanie is executed under the single-wire scheme – negative conclusions of sources and electric power consumers are connected to a body of the car which carries out function of the second wire. A food of all lighting devices and electric units is carried out from the battery of lead-acid type recharged from the generator of an alternating current.
The present section is devoted the description of procedures of service and repair of some elements of system of an onboard electric equipment. Besides, procedures of diagnostics of malfunctions of an electric equipment of the general order are considered.
On Audi device Controller Area Network (CAN) is established. It unites separate monitors in the general scheme (the tyre of the data) that offers following advantages: fast data transmission from one device to another, economy of a place at the expense of application of small payments and details, reduction of quantity of gauges at the expense of their multifunctionality.
Principle of work CAN
Instead of a separate conductor for each signal two general wires that allows to receive simultaneously the information on a condition of the majority of devices and gauges are used only, without using thus separate toggle-switches and switches.
Tyre CAN, receiving the important information (for example, about malfunction), fixes it in the memory.
At repair of an electric equipment and the engine power supply system disconnect a wire from the plug «–» the storage battery.
At replacement of safety locks it is forbidden to apply screw-drivers and the metal tool as it can lead to short circuit in electric equipment chains.
It is forbidden to disconnect the switchboard of ignition and the storage battery on the working engine as it will lead to failure of a regulator of pressure and elements of the electronic equipment of the car.
At check of chains of an electric equipment it is forbidden to close on "weight" of a wire (to check serviceability of chains «on a spark») as it can lead to failure of elements of an electric equipment.
It is forbidden even to connect quickly a conclusion «30» generators to "weight" (to check generator work «on a spark») as it will lead to failure of diodes выпрямительного the generator block. To check the generator on the car it is possible only the voltmeter and the ampermeter. In order to avoid failure of diodes выпрямительного the block it is forbidden to check them мегомметром or the control lamp fed with pressure more 12 In, and also to check such devices of a chain of an electric equipment on the car without a detachment of wires from the generator. To check resistance of isolation of a winding статора the generator the raised pressure it is necessary on the generator which has been removed from the car, at disconnected from выпрямительного the block winding conclusions статора.
At carrying out of electrowelding works on the car it is necessary to disconnect wires from plugs of the storage battery and the generator.
Do not concern elements of system of ignition and high-voltage wires on the working engine.
Do not lay a wire low and a high voltage in one plait.
At additional charge of the storage battery on the car with the help charger devices disconnect wires from battery plugs.
Stock-taking of pressure of a food
Stock-takings of pressure of a food are made in case of infringement of functioning of an electric chain. Connect one of wires of a tester of electric chains or to a negative pole of the storage battery, or to well earthed point of a body of the car. Other wire of a tester connect to the plug of an electric socket of a checked chain, it is preferable the nearest to the storage battery or a safety lock. If the control lamp of a tester lights up, pressure of a food on the given piece of a chain is present that confirms serviceability of a chain between the given point of a chain and the storage battery. Continuing to operate similarly, investigate the chain rest. Detection of absence of pressure of a food speaks about malfunction presence between the given point of a chain and last from checked up earlier (where pressure of a food was present). In most cases, a cause of a failure is easing of electric sockets and infringement of quality 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 a lamp-sampler or the voltmeter. Pressure in a chain should be absent. Pull conducting, observing of a lamp-sampler. If the lamp starts to blink, somewhere in the given plait of wires there is a short circuit on the weight, probably caused by wiping of isolation of wires. Similar check can be made for each of components of an electric chain by inclusion of corresponding switches.
Check of serviceability of grounding
The given check is made for the purpose of definition of reliability of grounding of an element of a chain. Disconnect the storage battery and connect one of wires of a lamp-sampler having the independent power supply to the obviously well earthed point. Other wire of a lamp connect to a checked plait of conducting or the plug of an electric socket. If the lamp lights up, grounding is perfectly in order (and on the contrary).
Checks on absence of breakage
Check is made for the purpose of revealing of breakages of an electric chain After switching-off of a food of a contour check up it by means of a lamp-sampler equipped with the independent power supply. Connect sampler wires to both ends of a chain if the control lamp lights up, breakage in a chain is absent. If the lamp does not light up, it testifies to presence in a breakage chain. In the similar image it is possible check up also serviceability of the switch, having connected a sampler to its plugs. While translating the switch in position "Vkl" the sampler lamp should light up.
Localisation of a place of breakage
At diagnostics of the suspect on presence of breakage of a site of an electric chain visually to find out a cause of defect it appears difficult enough as survey of plugs on presence of corrosion or infringement of quality of their contacts is complicated, in a kind of limitation of access to them (usually plugs are closed by the case of an electric socket). Sharp twitchings of the case of a socket on the gauge or a plait of its wires in many cases leads to contact restoration. Do not forget about it at attempts of localisation of a cause of a failure of the suspect on presence of breakage of a chain. Astably arising refusals can have the reason oxidation of plugs or infringement of quality of contacts.
Diagnostics of malfunctions of electric chains does not represent a stubborn problem under condition of that accurate representation that the electric current arrives to all consumers (a lamp, the electromotor, etc.) from the storage battery on wires through switches, the relay, safety locks, fusible inserts, and then comes back in the battery through weight of a body of the car. Any problems connected with refusal of an electric equipment can have the reason only stopping delivery on them of an electric current from the battery or its return to it.
Wires, safety locks and the relay
Protection of electric chains of the car against short circuit is provided with application of set of safety locks, breakers of chains and fusible inserts. The burnt down safety lock is easy for distinguishing from serviceable by survey of its transparent plastic case. Attentively examine a safety lock for its revealing перегорания. If the safety lock outwardly looks normally, but suspicions on its malfunction have remained, make conductivity check between ножевыми the plugs acting from its case.
At replacement of safety locks watch conformity of face value of a new safety lock to face value of the old. The safety locks calculated on a various current strength can look outwardly identical, therefore it is necessary to give special attention to marks. Replacement of the burnt down safety lock on calculated on smaller – and especially big – a current strength is undesirable. Each electric chain requires different degree of protection. Watch that marks on the safety lock case corresponded to a current strength on which the corresponding chain is calculated. If the replaced safety lock immediately fuses, it will be not reasonable to continue its replacement. First of all, it is necessary to reveal and eliminate its reason перегорания. In most cases that appears short circuit in the electric chain, caused by breakage or damage of isolation of a wire.
Protection of some electric chains is carried out by inclusion in them of fusible inserts. Inserts are usually used for protection of the chains which have been not equipped with safety locks, such as a chain of system of ignition.
Fusible inserts are similar to safety locks in the sense that their exit out of operation (оплавление) is easily defined visually.
For replacement of a fusible insert disconnect a negative wire from the storage battery. Take burnt down insert and establish on its place the new. Before insert replacement necessarily try to define the reason of the overload which have caused an exit of an insert out of operation.
Chain breakers (thermal relays)
Thermal relays serve for protection of such components, as electric drives windows, locks of doors and adjustment of position of headlights (electroproof-readers). Some of breakers of chains are established in the assembly block. Return of thermal relays to an initial condition on some models is carried out automatically, i.e. at overload occurrence in a chain the thermal relay is instantly disconnected, then, after cooling, reverts to the original state. If contour return into position does not occur, it is necessary to make its check immediately. Normal functioning of the thermal relay confirms serviceability of a contour. Some of breakers are equipped by buttons for manual compulsory return to an initial condition.