Troubleshooting electrical equipment (Scorpio 2)

When troubleshooting an electrical system, a systematic approach is important. This applies to both checking failed incandescent lamps and checking non-working electric motors.

If an electrical component is protected by a fuse, the first step is to check the fuse. The location of the correct fuse is determined from the diagram on the fuse box cover - see also chapter "Replacing fuses".

The defective fuse is replaced and after switching on the power consumer it is necessary to check whether the fuse has blown again immediately. If the fuse has blown again, the fault must be found and eliminated, as a rule, it is a short circuit. This means that in some place, perhaps also inside the device, the ground and the positive conductor are connected to each other.

The second step of checking is if the incandescent lamp does not light or the electric motor does not work with a working fuse, it is necessary to check for the presence of supply voltage.

Checking an incandescent lamp

Remove the lamp and inspect it. If the filament bulb is burnt out or loose in the base, it should be replaced.

To eliminate doubts about the serviceability of the lamp, proceed as follows: connect one conductor to the positive (+), and the other to the negative (-) pole of the battery, and connect the free ends of the conductors to the lamp. In this case, it does not matter how the conductors are connected to the lamp. One conductor to the current-supplying connector, and the other to the lamp body. If the lamp does not light, it should be replaced.

Note: Make sure that the contacts of the lamp and lamp socket are not rusted. If necessary, clean rusted or bent contacts and restore them to a perfect condition.

If the bulb is in good condition, insert the bulb and turn it on. If it does not light, use the test bulb to check for supply voltage. To do this, connect the test bulb to ground. This means that one wire of the test bulb must be connected to a reliable engine ground (clean metal surface) or directly to the negative pole of the battery. The other electrode of the test bulb (+) must be connected either to the current-carrying plug or inserted into the current-carrying wire. If the test bulb now lights up, but the incandescent bulb still does not light, then there is a break in the ground wire. To check this, install a jumper from the ground to the bulb socket. The bulb should light up.

Note: there are lamps to which voltage is supplied by only one conductor, for example, parking lamps, interior lighting of the car. These lamps are connected to the car ground directly by their housing. If the current-supplying conductor of the lamp has no voltage, that is, the control lamp does not light, it is very likely that the switch is faulty. Check the switch.

Checking Electric Motors

In order to increase comfort, more and more small electric motors are used in cars. They are used in mechanisms such as window lifters, in the drive of the sliding roof panel, in the electric central locking system or in the control of the electric antenna.



Each electric motor is turned on when needed by a switch, in most cases manually. In the case of an electric antenna, the switch is controlled automatically by the radio.

Check the fuse for the corresponding electric motor and replace the fuse if necessary.

Note: Before re-activating the electric window and central locking system, the cause of the electric motor overload must be eliminated. The overload may be caused by icing of the window panes and door locks or contamination of the window regulator guide rails.

If the fuse blows again immediately, a short circuit has occurred.

To definitely find out whether the pi electric motor is working properly, it is necessary to connect it with two auxiliary wires with a diameter of approximately 2 mm directly to the car battery. The positive pole of the battery must be connected to the positive connector of the electric motor, and the negative pole to the negative connector. In doubtful cases, the location of the positive and negative connectors of the electric motor is determined in accordance with the electrical diagram. If necessary, the electric motor is removed. All electric motors of the car are powered by an on-board voltage of 12 to 14 volts. If the electric motor now works normally, the cause of the malfunction was the lack of supply voltage.

Note: If the motor rotates slowly or intermittently, the carbon brushes may be worn out and should be replaced.

If the electric motor is running, use the electrical diagram to determine which conductor supplies voltage to it when the switch is pressed and before the ignition is turned on.



Check the supply wire with a test lamp. Since a large current flows through the electric motor, you can use a regular incandescent lamp as a test lamp. It is equipped with sharp electrodes that can be used to pierce the connecting wire. This allows you to easily determine the presence of supply voltage. Reversible electric motors, such as window lifters, have two positive connectors.

Note: Checking the windscreen wiper motor is described further in the relevant chapter.

If voltage is not supplied to the electric motor, the supply circuit is faulty. Find the fault in the wiring according to the electrical diagram and fix it. Electric motors, due to the need for high currents, usually have an additional switching relay. Checking the relay is described in the corresponding chapter.

If no fault was found, check the switch.

If there is a wire defect, it is advisable to lay a new wire, since it is quite difficult to localize the wire defect.

Checking the switch

Most electrical consumers are switched on and off manually via a switch. There are also switches that operate automatically. Such switches include, for example, hydraulic switches and brake fluid level switches.

The main function of a switch is to close and open an electrical circuit. There are switches that open the ground wire and switches that open the positive voltage wires.

Checking lamp switches and electric motors

Remove the corresponding switch.

Simple switches have only 2 wire connectors. In this case, positive voltage (+) is always supplied to one connector, and after the switch is turned on, positive voltage is supplied to the other connector. There are also switches with an increased number of connectors. According to the electrical diagram, you should find out to which connectors in such switches voltage should be supplied, if necessary, first turn on the ignition.



Use a test lamp to check whether voltage is supplied to the switch power connector. If the test lamp lights up, turn on the switch and check whether voltage is supplied to its output connector. If voltage is present, it can be concluded that the switch is in good working order.

If there is no voltage at the switch power connector, then there is a break in the current-supply circuit. In accordance with the electrical diagram, check the current-supply circuit and, if necessary, lay a new wire

Checking the sensor switches

Such switches include, for example, hydraulic switches and coolant and brake fluid level switches.

Connect a switch testing device (test lamp or ohmmeter) to the switch's inlet and outlet wires, for which one wire must be removed from the switch.

Note: Switches that are screwed into the engine block usually do not have a ground wire, since this function is performed by the switch housing.

When the switch is on, the test device should show the conductivity of the switch. This is best determined with an ohmmeter: when the switch is on, it should show 0 Ohms, and when it is off, it should show ∞ (infinity) Ohms.

The fastest way to check the operability of the coolant or brake fluid level indicator switch is to remove the power cable from the sensor with the ignition on and connect it to a reliable ground, such as the engine cylinder block. If the indicator lamp lights up, the switch is faulty.

A distinctive feature of the hydraulic switch: when the engine is not running, the switch contact is closed (the indicator lights up). Only at a certain pressure does the contact open and the indicator goes out.

Checking the relay

A relay is built into many electrical circuits. A switching relay works like a switch. Example: when the high beam is turned on manually, the relay receives a command to supply current to the high beam headlights. Of course, it would be possible to supply current to the high beam headlights from the battery directly through the light switch. However, all consumers that require a large current (high beam headlights, windscreen wipers, fog lights) include an intermediate relay in order not to overload the switch and to protect the circuit from short circuits. In addition to switching relays, there are also functional relays, for example, for the windscreen cleaning and washing system or a warning sound relay in the circuit for switching on the external lighting.

Checking the switching relay

When the corresponding consumer is switched on, the control function of the relay is activated. In this case, the coil of the electromagnet inside the relay attracts the contact and thus closes the electric circuit of the working current. The working current flows further through the relay to the consumer.

The easiest way to check the functionality of a relay is to replace it with a working one. This is what service stations do. Since a car owner only very rarely has a new relay at his disposal, the following sequence of operations is recommended with so-called switching relays, which are used to turn on fog lights and main lights. The terminal designations given below, especially for serially installed relays, may differ.



Remove the relay from the holder.

Turn on the ignition and operate the corresponding switch.

First, use a voltage tester to determine whether voltage is being supplied to the positive terminal (+) of the relay board. To do this, connect one electrode of the tester to ground (-), and carefully insert the other electrode with the sharp end into the terminal. If the LED of the tester lights up, then voltage is being supplied. If the tester shows no voltage, use the electrical diagram to find a break in the circuit from the positive pole (+) of the battery to the positive terminal.

Make a jumper from a piece of insulated wire, cleaning the ends of the jumper until shiny.

Connect the (+) terminal of the relay board (this terminal is always supplied with voltage from the positive pole of the battery) with the terminal at the relay output using this jumper. This operation does practically the same thing as a working relay does. Where the terminals are on the relay board can be determined by the color of the wires and the electrical diagram.

When, with the jumper installed, for example, the high beam lights up, we can conclude that the relay is faulty.

If the high beam does not light, you need to find out if the headlights are connected to ground properly. Then, using the electrical diagram, find and fix the break in the wiring from the relay terminal to the main headlights.

If necessary, install a new relay.

Checking the windshield wiper motor

The windshield wiper motor is located under the windshield in the water drainage casing. To check, the corresponding cover must be removed. The following is a description of the work applicable to the windshield wiper. For the rear window wiper, proceed in a similar manner.

Terminal Designations

The electric motor terminals are standardized.

• Terminal 31 is used to connect ground (in all automotive electrical equipment).
• Terminal 53 supplies voltage for the first windshield wiper speed.
• Terminal 53a receives positive voltage (+) to reset the windshield wiper to its original position; after the driver turns off the windshield wiper, the electric motor receives voltage through the brush until the windshield wiper blades are in the extreme lower position.
• Terminal 53b supplies voltage for the second windshield wiper speed (parallel winding).
• It is not always possible to use terminal 53e to brake the electric motor during the reverse stroke after switching off, so that the windshield wiper does not go beyond its stop position.
• Not always present, terminal 53c (from the relay) is connected to the electric window washer pump, terminal 53i is present in windshield wiper motors with a permanent magnet and a third brush (for high operating speed).

Checking the windshield wiper motor

First of all, it is necessary to find out whether the electric motor is faulty or there is no supply voltage. To do this, proceed as follows.

Disconnect the multi-pin plug connector from the electric motor.

Connect positive (+) and negative (-) voltage from the battery to the electric motor using two auxiliary wires.

• connect the wire from the positive pole to terminal 53 or 53b;
• connect the wire from the negative pole to terminal 31.

Now the windshield wiper motor should operate at first or second speed depending on the terminals involved. If this is not the case, the electric motor or its corresponding winding is faulty. Remove the windshield wiper motor, see p. 186.

Checking the flashing light

The flashing light and the hazard warning light system are switched on and off by means of a relay, the so-called turn signal interrupter. The hazard warning light system is connected to a relay without a fuse. The flashing light circuit of the turn signal is protected by a fuse located in the fuse box.

If the blinking rhythm of the turn signal lights on one side is faster than on the other, then there is a defective incandescent lamp or a broken wire in the place where the blinking is faster.

In most other cases, the cause of the malfunction is a defective turn signal relay. The location of the terminals (pins) of the turn signal flasher is designated:

• terminal 31 is used to connect the ground ("-" in all automotive electrical equipment);
• terminal 49 is the relay input (positive voltage is constantly supplied), and terminal 49a is the relay output.

If you don"t have a new relay, carefully insert a thin wire between terminals 49 and 49a of the relay plug.

Note: The contacts must not be damaged. Bend the ends of the wire before inserting to avoid sharp edges. Reinsert the faulty turn signal relay. The pins of the relay are long enough to allow this despite the jumper.

Turn on the ignition. If you now operate the turn signal lever, the turn signal lights on the corresponding side will be on continuously. The rhythm of turning the lights on and off can be created using the turn signal lever.

If, despite the jumper of the relay contacts, the turn signal lights do not light up, then the cause of the malfunction lies either in the turn signal switch or in the electrical wiring.

Checking the brake light

If the brake light does not come on, you should first check the condition of the fuse in the fuse box.

If the fuse is OK, then you need to check the brake light bulbs and replace them if necessary.

If the brake light bulbs are OK, you should check the brake light switch. The switch is located on the pedal bracket above the brake pedal. When you press the brake pedal, the contact pin extends out of the switch. The switch contact closes and the brake light comes on.

Check the brake light switch. To do this, disconnect the 2 plug connectors of the switch.

Turn on the ignition.

Make a jumper between the contacts of both plugs using a short auxiliary wire. If the brake light comes on, the brake light switch is faulty.

Replace the brake light switch.

[The original article is available on the website Fordbook.ru]