Audi A4, S4

Since 2000 of release

Repair and car operation

Diagnostics of malfunctions of an onboard electric equipment - the general information

Procedures and codes of diagnostics of systems of electronic control are considered in the Head of System of an electric equipment of the engine.

The structure of a typical electric contour can include an electric component, various switches, the relay, electromotors, safety locks, fusible inserts or the breakers of the contour concerning the given component, and also conducting and the electric sockets serving for connection of a component with the battery and weight of a body. For simplification of a problem of search of malfunctions of electric contours in the end of the Management basic schemes of electric connections are enclosed.

Before starting works on elimination of malfunctions any of electric contours, attentively study the corresponding scheme as more as possible to be clear in the mind about its functional purpose. Narrowing of a circle of troubleshooting is usually made for the account of gradual revealing and an exception normally functioning a component of the same contour. At simultaneous failure at once a several component or contours most a refusal plausible reason is blowing a corresponding safety lock or grounding infringement (different contours in many cases can become isolated on one safety lock or the weight plug).

Electric equipment refusals frequently speak the elementary reasons, such as corrosion of plugs, safety lock failure, combustion of a fusible insert or defect of the relay of switching. Make visual check of a condition of all safety locks, conducting and electric sockets of a contour before starting more concrete check of serviceability its component.

In case of application for troubleshooting of diagnostic devices carefully plan according to applied electric schemes in what points of a contour and in what sequence it is necessary to connect the device for the purpose of the most effective revealing of defect.

The number of the basic diagnostic devices includes a tester of electric chains or the voltmeter (it can be used also 12 In a control lamp with the complete set of connecting wires), the indicator of conductivity of a piece of a contour (sampler) including a bulb, own power supply and the complete set of connecting wires. Besides, always it is necessary to have in the car the complete set of wires for start of the engine from the auxiliary source, equipped with clips of type a crocodile and, it is desirable, the breaker of a contour which can be applied to shunting and connection various a component of an electric equipment in the course of contour diagnostics. As already it was mentioned above before starting check of a chain by means of the diagnostic equipment, define under schemes of a place of its connection.

Pressure stock-taking

Pressure stock-takings are made in case of infringement of functioning of a contour. Connect one of wires of a tester of electric chains or to a negative pole of the 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 contour, it is preferable the nearest to the battery or a safety lock. If the control lamp on a tester lights up, pressure on the given piece of a chain takes place that confirms serviceability of a contour between the given plug and the battery. Continuing to operate in a similar manner, investigate the contour rest. Revealing of absence of pressure speaks about malfunction presence between the given point of a contour and last from checked up earlier (where pressure was present). In most cases a cause of a failure is easing of electric connections and infringement of quality of contacts.

Remember that a food on some of contours of an onboard electric equipment moves only in ignition key "АСС" positions (Lay) or «RUN» (Movement).

Short circuit searches

One of methods of searches of short circuit is extraction of a safety lock and connection instead of it a lamp-sampler or the voltmeter. Pressure in a contour should be absent. Pull conducting, observing of a lamp-sampler. If the lamp starts to blink, somewhere in the given plait there is a short circuit on the weight, probably caused by wiping of isolation of a wire. Similar check can be made for each of a contour component, including switches.

Check of serviceability of grounding

The given check is made for the purpose of definition of reliability of grounding of a component. Disconnect the battery and connect one of wires of the lamp-sampler equipped with the independent power supply to the obviously well earthed point. Other wire of a lamp connect to a checked plait or the plug. If the lamp lights up, grounding is perfectly in order (and on the contrary).

Conductivity stock-takings

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 battery. Connect sampler wires to both ends of a contour (or by "the power" end (+) and to well earthed point of a body) if the control lamp lights up, breakage in a contour is absent. Refusal of inclusion of a lamp testifies to infringement of conductivity of a chain. In the similar image it is possible to check up and serviceability of the switch, having connected a sampler to its plugs. While translating the switch in position "Vkl" the control lamp-sampler should light up.

Breakage localisation

At diagnostics of the suspect on presence of breakage of a contour 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 socket case). Sharp twitchings of the case of a socket on the gauge or a plait of its wires in many cases leads to conductivity restoration. Do not forget about it at attempts of localisation of a cause of a failure of the suspect on contour breakage. Astably arising refusals can have the reason oxidation of plugs or infringement of quality of contacts.

Diagnostics of malfunctions of electric chains at all does not represent a stubborn problem under condition of accurate representation that the current arrives to all electric loadings (a lamp, the electromotor, etc.) from the battery on wires through switches, the relay, safety locks, fusible inserts, and then comes back in the battery through weight 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.