Citroen Xantia

since 1993 of release

Repair and car operation

Search of causes of failures of 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).

General information

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

Before starting identification of causes of failure of the failed electric device, attentively study the corresponding electric circuit. Try as it is possible to imagine more clearly a principle of functioning of the components which are a part of this contour. The list of possible causes of failure can be minimized by a way of an exception of it unequivocally regularly functioning components concerning work of the checked chain. At simultaneous violation of functioning at once several components or contours, the most probable cause of refusal is failure of the general for these contours of a safety lock, or grounding violation.

More often refusals of electric equipment speak the elementary reasons, such as oxidation or weakening of fastening of terminal connections, failure of a safety lock or a fusible insert, failure of the relay, etc. Before starting search of internal defects of actually refused component, attentively check a condition of all safety locks concerning its functioning, contact sockets and electroconducting. For definition of the list of knots subject to check and terminal connections study the corresponding electric circuit (see. Removal and installation of components of a safety cushion).

It is necessary to carry to number of the main tools necessary by search of refusals of electric equipment:
   a) A measuring instrument of a chain or the voltmeter (the usual 12-voltny lamp also will be suitable for some checks with a set of connecting wires);
   b) A lamp sampler with the individual power supply (sometimes called also a conductivity measuring instrument);
   c) Ohmmeter;
   d) Battery;
   e) Set of connecting wires;
   f) A set of the wires crossing points, 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 starting actually performance of checks, attentively study the corresponding Schemes of electric equipment.

The simplest check of a chain which is carried out by twitching of various sites of electroconducting of the corresponding contour can be made for search of the reason of refusal having unstable character (refusals such usually appear connected with oxidation or weakening of fastening of terminal connections). As a result of such check it is possible to localize a defective piece of a chain. This check can be made in addition to any of listed below in the corresponding subsections.

Except the problems connected with violation of quality of electric connections, it is necessary to refer breaks and short circuit to number of the most probable and often meeting refusals of electric chains.

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

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

Search of breaks of a chain

PERFORMANCE ORDER

1. For chain check on break 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.
2. The second wire of the device connect to the terminal connection of a checked contour preferably closest to the battery or a safety lock.
3. Submit a food to a contour. Do not forget that some of chains запитываются only in certain positions of the switch of ignition.
4. If tension takes place (the measuring instrument lamp joins, or on the indicator of the voltmeter the corresponding indication is fixed), means, the chain piece between checked terminal connection and the battery is serviceable.
5. Continue check, serially passing from one terminal connection of a chain, to another (moving in the direction from a battery/safety lock).
6. The faulty site of a contour will lie between a point on which the device will not register existence of tension and last of the checked serviceable terminal connections. More often electroconducting break, or oxidation/weakening of fastening of the plug appears a cause of infringement.

Identification of the reasons of short circuit

PERFORMANCE ORDER

1. First of all disconnect the consumer (and) the electric power of a checked contour (consumers of the electric power, or components for which functioning energy of a current circulating in a chain, such as lamps, electromotors, heating elements, etc. is spent are called as useful loading of a contour).
2. 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.
3. Include power supply giving in a contour. Remember that some of chains запитываются only in certain positions of the switch of ignition.
4. If tension takes place on safety lock plugs, means, in a chain short circuit takes place.
5. If tension is absent, however the safety lock still fuses when giving food in a chain internal defect of the consumer (it) the contour electric power, therefore, takes place.

Identification of violations of grounding

The negative plug of the battery is earthed on metal of the power unit called in "mass", the chassis and body elements of the car. Electric contours of the most part of electric equipment 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 form themselves a returnable part of a chain. In view of the aforesaid, weakening of fastening or development of corrosion of basic elements of a working component of a chain involves violation 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 weakening of fixture of devices 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 violation of functioning of the another which outwardly in any way has not been connected with failed. Pay attention that on many cars certain knots are connected among themselves by special tires of grounding. Such tires 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 fastening of the power unit to the car chassis).

PERFORMANCE ORDER

1. 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 car. 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 serviceability of connection (see the following item).
2. In the presence of suspicions on violation of quality of terminal connection of grounding, disassemble contact knot and smooth out to naked metal interfaced surfaces of plugs. Try to remove completely all traces of corrosion and dirt, then scratch out a knife paint, achieving unequivocal contact of metal surfaces. At assembly of knot take care of durability of a tightening of fixture. Between plugs of electroconducting and contacts of weight lay washers with a notch for completeness of a quality assurance of electric connection. In order to avoid corrosion development in the future cover the connected terminal knots with acid-free vaseline or silicone greasing. Good means are also the aerosol, applied to sealing of components of system of ignition and water-repellent greasing.