Introduction

INTRODUCTION

ELECTRIC MOTORS/SOLENOIDS

The electric motors and solenoids are mechanisms consisting essentially of electric windings; therefore the function test consists in verifying that the electrical continuity is undamaged in these windings; therefore use a tester as described previously.

It is also possible to check with the component installed in the car: disconnect and check the operation (for example motor rotation) connecting a 12 V source to the terminals.

The normal d.c.motors reverse the direction of rotation when the polarity is reversed:

therefore be careful to connect the two terminals correctly, using a polarity detector.

EARTH POINTS

An earth point is not correctly connected if there is oxidation, if it is not well tightened on its anchorage to the car body, if the cables arriving to it are uncovered or damaged.

To check whether an earth point is really at “potential 0”, connect one of the ohmmeter tester tips to it; connecting the other tip to the battery negative pole the resistance value read should be exactly 0 Ohm; if it is not, carefully check the earth point since it is faulty.

WELDINGS

In the car wiring there are many weldings between several wires: these are performed using the ultrasonic technique, thus obtaining very reliable and safe cos”.

To check a welding, just check the continuity of the wires that converge on it. It is not possible to repair a welding and should it happen - which is most improbable - that a welding is found damaged, it is necessary to replace the wiring.

CONTROL UNITS AND ELECTRONIC DEVICES GENERALLY

Today the electronic control units are the most important component part of the car. For this reason the reliability of the control units is very high, since the protection circuits have been specifically designed for this purpose.

The electronic control units, due to their complexity require the use of special equipment for the diagnostics, since it is not sufficient, nor advised to use a tester.

Several of the control units are fitted with an internal diagnostics system, that can be used connecting it through the diagnostic connector with Examiner or other diagnostic equipment.

In this way the information can be found that is memorised in the control unit, concerning the operation state, the checked parameters and any faults on the control unit itself, or on system components, as well as in the connections between the control unit and these components.

After the faults have been repaired, those memorised by the control unit can be erased.

It is also possible to run “active diagnostics”, i.e.simulation of a component operation(actuator) controlled by the control unit, checking the integrity and efficiency .

However, it is not possible to deal with these components generally, and it is therefore necessary to refer to the individual descriptions of operation.

IMPORTANT NOTE: it is never possible to intervene inside these electronic components, therefore, once it has been ascertained that they are not operating correctly they must be replaced.