- In the mounting blocks behind the left and right end trims of the instrument panel (sB/SC fuses);
- In the electronics unit on the left side of the air intake chamber (fuses S and relays);
- In the mounting block behind the upper trim under the steering column (fuses BG, 1b-6b, A1-D1 and relays);
- In the main fuse box under the driver's seat (sD fuses and relays);
- In the mounting block behind the right luggage compartment trim panel (sF fuses and relays).
2. The purpose of the fuses is indicated on the back of the cover of each mounting block. The fuse or relay number is indicated directly on the mounting block, next to the corresponding relay or fuse.
3. To gain access to the fuse boxes on the left/right side of the instrument panel, remove its left/right end trim (see Section 14 of Chapter 10). On the back side of the left end plate there is a tweezers for removing fuses.
4. To gain access to the mounting block in the luggage compartment, remove the right luggage compartment trim panel. The mounting block in the air intake chamber is accessible after removing the air intake chamber cover (see Section 19 of Chapter 1).
Fuses
5. Each individual fuse is used to protect a specific electrical circuit or several circuits at once, and one circuit may have one or more fuses. Fuses in mounting blocks are mostly compact in design, equipped with bayonet contacts and, if necessary, easily removed from their sockets with fingers or pliers stored in the cover of the mounting block. To remove the fuses, use the pliers stored in the mounting block behind the left end cover. For small fuses, slide the tweezers from above, and for large fuses, slide them from the side.
6. If any of the electrical consumers fails, the condition of the corresponding fuse should always be checked first. Turn on the ignition and use a test lamp to probe the open terminals of each fuse. If the lamp lights when connected to each terminal, then the fuse is good. If voltage is present only on the power supply side, then the fuse has blown. It should also be noted that the fuse housing is usually made of transparent plastic, through which it is easy to determine the state of the working jumper.
7. When replacing a blown fuse, make sure that the replacement element you prepare matches the type of the defective one. Fuses rated for different current ratings may not physically differ from each other, but are not interchangeable. Each electrical circuit has different operating parameters and requires a different degree of protection, so replacing a fuse rated for a certain current with a fuse with inappropriate parameters is fraught with the most serious consequences (until a fire breaks out). The operating parameters of the fuse are usually indicated on its plastic housing, and color identification is also used.
8. If a new fuse also fails immediately after installation, there is no point in replacing it further; the cause of the overload in the circuit must first be identified and eliminated. In most cases, this is a short circuit in the connecting wiring caused by damage to its insulation. Spare fuses are usually located in the available terminal blocks.
Relay
9. To supply power or control signal to some of the electrical consumers in the vehicle (such as fuel injection system components, horn, starter, cooling fan, fog lights, and others) relays are used. In fact, the relay is an electrical switch that ensures the closing of the working circuit according to the control signal. If the relay fails, the corresponding consumer will not function. A description of how to check the proper functioning of the relay is given below. Failed relays must be replaced.
10. If it is not possible to find out how to connect the relay to the corresponding electrical circuit using the electrical connection diagrams (diagrams are provided at the end of the manual), it should be remembered that the approach to testing any relay is, in principle, the same in all cases (see below).
11. In most cases, a control circuit is always connected to two of the relay contact terminals. When control voltage is applied to these terminals, current begins to circulate through the relay control winding, resulting in the closing of the contacts of the working circuit of the power consumer. The remaining terminals are the working circuit terminals.
12. To facilitate identification of relay terminals, explanatory markings with an image of the key connection diagram are usually applied to its housing.
13. Before removing the relay, make sure that the corresponding circuit is de-energized.
14. Connect a fused jumper wire between one of the relay control terminals and the positive battery terminal. Using a second jumper wire, ground the second control terminal - the relay should click. Some relays require that the polarity of the connection be strictly observed. If there is no click, try reversing the polarity of the control terminals.
15. With the jumper wires connected, check for continuity between the terminals of the working circuit.
16. If the test result is negative, replace the relay.
[The original article is located on the online resource: AudiManual]