The battery supplies current to the ignition system, lighting devices and other electrical consumers and has a capacity reserve in case the consumed current exceeds the current coming from the generator.
The alternator has its own regulator that provides high output power when the battery is weak and current draw is high, and low output power when the battery is fully charged and draw current is low.
When connecting electrical components to the vehicle's on-board network with a grounded «minus» it is very important to connect them correctly if they contain silicon diodes or transistors, as if connected incorrectly, these elements may fail. This applies to radios, tape recorders, electronic ignition systems, electronic tachometers, electronic corrosion protection devices, etc. - they must all be connected with the correct polarity.
It is important to know that the positive cable to the battery must always be disconnected if the battery is being charged in the vehicle. If welding is carried out using electric welding, then the generator must also be turned off to avoid serious damage. Always make sure that the battery contacts are properly connected to their respective wires. When working on electrical parts, it is recommended to disconnect the negative cable from the battery.
Checking lamps
After removing the lamp, inspect it. If the filament is burned out or the glass bulb is loose on the base, replace the lamp.
Accurate test of the lamp: connect the pump through the wires to the battery. In this case, the polarity is not important. If the lamp does not light up, replace the lamp. Check for corrosion on the wire contacts and on the lamp socket. Clean up contacts.
The probe lead must be connected to a reliable ground (bare metal) or to the negative battery terminal. test needle (+) hold on the current-carrying contact of the connector or pierce the current-carrying wire with it. If at this time the probe lights up and the lamp does not light, then there is an open in the lamp ground wire. To check this, connect a ground with an auxiliary wire to the lamp socket. The lamp should light up.
Lamps that have only current-carrying wiring are connected to the vehicle ground directly through their housing.
In the absence of voltage in the current-carrying wire of the lamp (probe does not light up) possible switch failure. Check switch.
Checking electric motors
Electric motors perform a lot of functions in a car:
Check or replace the motor fuse.
The electric motors for the power window and the sunroof have automatic fuses that are switched off from overloads and turn on after a while. The reason for the deviation may be frozen glass or dirty window rails.
A fuse blowing again indicates a short circuit.
To accurately determine the defect of the motor, connect the motor with two wires with a diameter of about 2 mm to the battery. Positive wire to the positive terminal, negative wire to the negative terminal of the motor. If the engine runs well, then the defect was in the power supply. Slow and intermittent rotation of the motor indicates worn carbon brushes. Replace brushes.
If the motor is running, determine (according to the electrical diagram) a wire that supplies power when the switch is turned on, and before that the ignition is turned on.
Check the lead wire. As a probe, you can use an ordinary incandescent lamp, with a sharp needle at the end of the wire of which you can pierce the wire.
If there is no voltage at the motor terminals, the power supply is defective. Determine the defect using the electrical diagram and eliminate it. Motors are often switched on via an intermediate relay, so the relay should be checked.
Finally check the switch.
If the wire is damaged, it is better to lay a new wire.
Checking switches
The function of switches is to close or open an electrical circuit. Some electrical consumers are switched on and off manually. There are switches that work automatically. There are switches that switch the ground wire, and switches that cut off the supply current.
Checking lamp switches and electric motors
For switches with multiple terminals, refer to the wiring diagram for which terminal should be energized.
Check the voltage supply to the switch with a tester. If the lamp lights up, turn on the switch and check for voltage at the output terminal. If there is voltage, the switch is working.
The absence of voltage at the input terminal indicates a break in the current lead. Check the voltage supply according to the wiring diagram and lay a new wire if necessary.
Checking the sensors-switches (signaling devices)
Switch sensors include, for example, oil pressure sensors and coolant or brake fluid level sensors.
Connect a probe or ohmmeter to the sensor terminals by removing the wires from them. V sensors mounted on the propulsion unit, the sensor housing serves as a ground pole.
When the switch is closed, the instrument should indicate a short circuit. With the switch closed, the ohmmeter should show 0 ohms, with the switch open, infinity.
It is more convenient to check the serviceability of the coolant and brake fluid level sensors by removing the wire from the switch with the ignition on and connecting it to ground, for example, on the engine block. The burning of the control lamp on the dashboard indicates a malfunction of the switch.
When the engine is not running, the contact of the oil pressure sensor is closed (control lamp on), the switch opens only at a certain pressure.
Relay test
In cars, turnips work in many electrical circuits: an intermediate relay, functional relays and a warning signal relay, etc.
Checking the enable relay
When the power consumer is turned on, the operating current flows to it through the relay.
The easiest way to test the relay is to replace it with a known good one. But there is not always an extra relay, so the following method is proposed for the on relay and fog lights.
Remove the relay from the block.
Turn on the ignition and the corresponding switch.
Check the presence of voltage on the positive terminal with a probe. Otherwise, find an open in the electrical circuit between the battery and the terminal.
From an insulated wire, make a jumper, exposing the ends, connect the jumper on the relay block to the positive terminal of the battery with the turnout output contact, which achieves the effect, as if a replacement was made with a known-good relay. The location of the terminals on the relay block is determined by the color of the wires, or by the electrical diagram.
If the high beam headlights come on with a jumper, the relay is faulty.
If high beam fails, check headlight ground connection. Then, using the electrical diagram, find and repair the wire break.
Install a new relay if necessary.
Checking the wiper motor
The wiper motor is located in the water collection compartment under the windshield, the rear window wiper is located in the tailgate. To check it is necessary to remove the corresponding casing.
Typical windshield wiper test
To determine if the wiper motor or power supply is defective, proceed as follows:
Remove the wiper motor connector.
Connect with auxiliary wire (+) battery terminal with terminal 1. (The negative terminal of the motor is already connected to the terminal (-) battery through body).
The wiper motor should run slowly. Otherwise, it is a failure of either the motor or the 1st stage of the switch.
By connecting the positive wire together with terminal 1 to terminal 2 on the right, the wiper motor should start at speed II.
With non-durable connections, start the motor from any position, except for the end position.
Bridge terminals 1 and 3.
By connecting the positive terminal of the battery to terminal 4, check the stop of the engine in the end position after it has started.
Typical rear window wiper test
Connect the battery plus to pin 1 of the connector and check that the motor is running. Then, by connecting pins 2 and 3, connect the battery plus to pin 1, while the motor should start and stop in the end position.
If the motor does not work properly, install a new one.
Checking the turn signal breaker
The alarm interrupters and the vehicle's direction indicators are protected by different fuses.
With an uneven rhythm of blinking on different sides, it should be assumed that on «rapid» board, one of the lamps is defective or a wire is broken.
The cause of other malfunctions is the breaker relay. To check, remove the turnip. Using auxiliary wires, connect the relay contacts 1 and 2 with the battery, connect two incandescent lamps for direction indicators connected in parallel to contacts 1 and 2. The lamps should flash at a frequency of 60 to 120 times per minute. Replace the breaker if this condition is not met.
If there is no new relay, you can insert a thin wire between pins 2 and 3 in the turnip connector. Before inserting, bend the ends of the wire. Insert the defective turnip again
Turn on the ignition. When the turn signal switch is switched, the turn signal lamps are now permanently on. By quickly turning the switch on and off, you can simulate the operation of an interrupter. But this is a temporary replacement.
If the direction indicators do not light up and with a jumper, then the cause of the malfunction should be sought in the switch or in the wiring.
Stoplight test
Check the fuse in the fuse box.
If the fuse is bad, check or replace the brake light bulb.
If the brake lights are not damaged, check the brake light switch, which is located on the bracket above the brake pedal. When you press the pedal, the push pin comes out of the switch. The switch contact closes and the brake light comes on.
To test the brake light switch, disconnect the two cable connectors from it.
Turn on the ignition.
If the brake light comes on when the jumper closes both pins of the connector, then the brake light switch is faulty, it must be replaced.
Checking the rear window heater
If the rear window heater malfunctions, check the fuse in the fuse box.
With a good fuse, check the connector at the rear window, there should be no corrosion on the connector.
If the heated rear window does not work after this, check the switch and wiring.
Check the operation of the enable relay.
If the heating element breaks, silver conductive paint can be used to restore the connection («silver coin»).