Fuses
Fuses are used to interrupt a circuit when the current exceeds a certain value and to protect components and wires that could be damaged by too much current. A sudden increase in current is usually caused by a fault in the circuit, most often a short circuit. The fuse box is located under the dashboard on the driver's side.
Each fuse protects its own circuit, and its belonging to a particular circuit is indicated on the fuse box cover.
Fig. 7.2. Example of a working and faulty fuse
The fuse box contains blade fuses, the color of which corresponds to the fuse protection current. In the event of failure of any element of the electrical equipment, the condition of the fuse should be checked first. The serviceability of the fuse is determined by the presence of a wire conductor connecting the fuse contacts (Fig. 7.2).
Fig. 7.3. Special tweezers for removing fuses
To replace a faulty fuse, first turn off the corresponding electrical circuit and remove the fuse from the socket using tweezers (Fig. 7.3).
If a newly installed fuse immediately blows when voltage is applied, check the protected electrical circuit. If the fuse protects several circuits, they must be connected one by one so that the faulty circuit can be determined by the blown fuse.
The heater and air conditioner draw a lot of current, so the fuse box has a switch to protect their circuits. If the circuit is opened by the switch, turn off the heater and air conditioner before pressing the reset button on the switch.
Relay
A relay is an electronically controlled switch that is typically used as follows:
- switches large currents remotely from the circuit in which the current flows, allowing the use of thinner wires and switch contacts;
- has more than one control input, unlike a mechanical switch;
- performs the function of a timer, for example, sets the interval for the windshield wipers to operate.
If the electrical circuit controlled by the relay fails and the relay is probably the cause of the fault, listen to the relay while the system is on. If the relay is working properly, you should hear a click when it is turned on. If the relay is working properly, the fault lies in the components or connecting wires. If the relay does not work, it is not receiving the main power or control pulse, or the relay is faulty.
Most relays are installed in the fuse and relay box located in the engine compartment.
Some specialized relays are located separately or in separate blocks under the instrument panel and in the engine compartment.