Skoda Felicia

Since 1994 of release

Repair and car operation

Search of causes of failures of an electric equipment

Described below procedure allow to make the general diagnostics of a condition of the main electric contours, however should not be applied to check of electric systems open to injury (such as, for example, ABS), in particular, including in the structure electronic modules of management (ECU).

The general data

The typical electric contour consists of the electric power consumer (a working component), switches of management (keys), the relay, electromotors, safety locks, the fusible inserts/breakers of the chain concerning work of the given component, and also connecting electroconducting, its contact plugs and sockets. For the purpose of simplification of performance of diagnostic procedures in the end of the given Chapter schemes of electric connections of various systems of an electric equipment of the car are resulted.

Before to start troubleshooting of the refused electric device, attentively study the corresponding electric scheme. Try as it is possible to imagine more clearly a principle of functioning of the components which are a part of the given contour. The list of possible causes of a failure can be shown to a minimum by an exception of it of the unequivocally regularly functioning components concerning work of the checked chain. At simultaneous infringement of functioning at once several components or contours, most a refusal plausible reason is failure of the general for the given contours of a safety lock or grounding infringement.

More often electric equipment refusals speak the elementary reasons, such as oxidation or fastening easing клеммных connections, failure of a safety lock or a fusible insert, relay refusal (the description of procedures of check испрвности relay functioning is resulted in Section Safety locks, the relay and breakers - the general information), etc. Before to start search of internal defects of actually refused component, attentively check up a condition of all safety locks concerning its functioning, sockets and wires. For definition of the list of knots subject to check and клеммных connections study the corresponding electric scheme.

It is necessary to carry to number of the basic tools necessary by search of refusals of an electric equipment:

a) the Measuring instrument of a chain or the voltmeter (for some checks usual 12-voltnaja the lamp with the complete set of connecting wires also will approach);
b) the Lamp-sampler with the individual power supply (sometimes named also a conductivity measuring instrument);
c) the Ohmmeter;
d) the Battery;
e) the Complete set of connecting wires;
f) the Set of the wires-crosspieces, equipped various type connecting plugs and, it is desirable, equipped with the breaker of a chain or a safety lock (for shunting of suspicious sites of a chain or electric components).

Before to start actually performance of checks, attentively study corresponding (from resulted in the end of the present Chapter) schemes of electric connections.

The elementary check of a chain which are carried out by twitching of various sites of electroconducting of the corresponding contour can be made for search of the reason of refusal having astable character (infringements such usually appear connected with oxidation or fastening easing клеммных electroconducting connections). As a result of such manipulations frequently it is possible to localise a defective piece of a chain. The given check can be made together with any of listed more low in corresponding subsections.

Except the problems connected with infringement of quality of electric connections, it is necessary to carry breakages and short circuits to number of the most probable and often meeting refusals of electric chains.

Chain breakage is usually defined by mechanical damage токопроводных veins or a detachment of contact plugs that leads to disconnection of a contour and the termination циркулирования in it of an electric current. As a result of chain breakage its working component ceases to function, however corresponding safety locks / fusible inserts do not fail.

As short circuit is called unforeseen a design of a chain short circuit of its electroconducting. Thus the current starts to circulate on the shortest way, usually leaving on weight. Short circuits are usually connected with infringement of integrity of isolation of electroconducting and without fail lead to failure of safety locks / fusible inserts of a chain.

Search of breakages of a chain

For contour check on breakage connect one of wires of a measuring instrument of a chain or the voltmeter to the negative plug of the battery or any of reliably earthed points on the chassis or the car engine.

The second wire of the device connect to клеммному to connection of a checked contour, preferably, to the nearest to the battery or a safety lock.

Include a food - do not forget that some of contours запитываются only in certain positions of the switch of ignition.

If pressure takes place (the measuring instrument lamp joins, or on the voltmeter indicator the corresponding indication is fixed), the chain piece between checked клеммным connection and the battery means is serviceable.

Continue check, serially passing from one клеммного chain connections, to another (moving to a direction from the battery/safety lock).

The faulty site of a contour will lie between a point on which the device will not register presence of pressure and last of checked up serviceable клеммных connections. More often electroconducting breakage, or oxidation/easing of fastening of the plug appears a cause of infringement.

Search of the reasons of short circuit

First of all disconnect the consumer () the electric power of a checked contour (electric power consumers, or as useful loading of a contour are called components for which functioning the basic share of energy of a current circulating in a chain, such as lamps, electromotors, heating elements, etc. is spent).

Take a safety lock of protection of a checked contour and connect to its adjusting plugs a measuring instrument of a chain or the voltmeter.

Include a food - remember that some of contours запитываются only in certain positions of the switch of ignition.

If pressure takes place on safety lock plugs, means, in a chain short circuit takes place.

If pressure is absent, however the safety lock on the former fuses at food giving in a chain, internal defect of the consumer (it) the contour electric power hence takes place.

Search of infringements of grounding

The negative plug of the battery is earthed on metal of the power unit named in "weight", the chassis and кузовных car elements. Electric contours большей electric equipment parts are constructed in such a manner that connecting electroconducting is used only for food giving to the consumer from the positive plug of the battery, return of a current to the battery is carried out on weight metal. It means that fixing elements of consumers of the electric power form themselves a returnable part of a chain. In view of the aforesaid, easing of fastening or development of corrosion of basic elements of a working component of a chain involves infringement of serviceability of functioning of a contour from a full exit of the last out of operation, before partial refusal of various sites of a chain. In particular, as a result of fixture easing brightness of a luminescence of lighting devices (can decrease in particular at the general grounding with other contour) or speed of rotation of the electromotor (for example, a drive of screen wipers or the fan of system of cooling). Thus refusal of one contour can cause infringement of functioning of the another which outwardly in any way have been not connected with failed. Pay attention that on many cars certain knots are connected among themselves by special tyres of grounding. Such tyres are used when there is no direct contact of metal parts of blocks in view of the equipment of support elastic rubber pillows and plugs (as for example, in support of a suspension bracket of the power unit).

For check of serviceability of grounding of a component disconnect the battery and connect one of ohmmeter wires to the obviously reliably earthed point of the chassis or the power unit. The second wire of a measuring instrument connect to a point of grounding of a checked component. The device should fix zero resistance, otherwise it is necessary to check up serviceability of connection.

In the presence of suspicions on quality infringement клеммного grounding connections, disassemble contact knot and smooth out to naked metal interfaced surfaces of plugs. Try to remove completely all traces of corrosion and a dirt, then scratch out a knife a paint, achieving unequivocal contact of metal surfaces. At knot assemblage take care of durability of a tightening of fixture. Between plugs of electroconducting and weight contacts, for the quality assurance of electric connection, lay washers with a notch. In order to avoid corrosion development in the future cover connected клеммные knots бескислотным with vaseline or silicone greasing. Good means are also the aerosol applied to hermetic sealing of components of system of ignition and water-repellent greasing.