Colour coding of fuses
- light brown - 5.0 A;
- brown - 7.5 A;
- red - 10.0 A;
- blue - 15.0 A;
- yellow - 20.0 A;
- green - 30.0 A;
- orange - 40.0 A.
Fusible links are used to protect electrical circuits that do not have fuses, such as the engine ignition system. The peculiarity of their replacement is that it is necessary to accurately determine the cause of its failure (overloads) and first disconnect the power source - "-" terminal from the battery. Breakers provide protection of electric motors from overloads and are installed in the drive circuits of window lifters, automatic door locks and headlight adjustment. Thermal relays are used as breakers.
Relays are designed to supply power to individual elements of electrical equipment. Many electrical circuits are laid through relay contacts and violations of the initial state of the relay contacts (sticking) lead to failure of the unit or assembly. A faulty relay must be replaced. The serviceability of the relay is checked by replacing it or laying temporary circuits (jumpers) for its power supply and operation. If a periodic malfunction occurs, as a rule, the culprit is a faulty relay.
Check the incandescent lamps by removing them and visually inspecting the integrity of the filament. A darkened bulb and a broken filament indicate that it has burned out. The simplest way to check is to connect the lamp directly to a voltage source of "+12 V". If the lamp lights up, this indicates a poor contact in the power supply circuit - the switch or base on the car - or a break in the power supply circuit. Check the switch by measuring the presence of the supplied voltage (+12 V) at its input terminals and, when on, at the output terminals with a test lamp or indicator. The absence of output voltage indicates a faulty switch, the absence of input voltage indicates damage to the power supply circuit. Check the electric motors by directly supplying power "+12 V" - "+14 V" using additional wires. In this case, it is necessary to strictly observe the polarity. One of the reasons for the failure of the electric motor is the wear of its brushes. The cause of blown fuses and fusible links in the electric motor power supply circuit is overload caused by contamination or icing of the guide elements in the drive (glass, roof, windshield wipers).
Electrical switches such as pressure or liquid level sensors must be tested on bench equipment after they have been removed.
The brake light should be checked in two directions. The first is a malfunction of the lamp itself and its power supply circuit. The second is the functioning of the brake pedal contact block. To access the block, it is necessary to remove the lower panel of the steering control (see the sections "Brake system" and "Steering"). The electric rear window heater should be checked in two directions. The first is the serviceability of the power supply circuit - wire, BS and switch. The second is the integrity of the rear window heating element. If the heating threads are broken, it can be repaired by using conductive varnish ("zilbert varnish"). Clean the damaged area with solvent or acetone. Select the area to be repaired with adhesive tape so that it is located between the two tapes. Apply the varnish and let it dry for 24 hours at a temperature of +20°C, or for 30 minutes at a temperature of +150°C, using an industrial hair dryer.
[The original material is located on the website «BMWMAN»]