Attention. If you are repairing any car systems, and even more so electrical equipment, then do not forget to disconnect the wire before starting work "masses" battery.
When replacing blown fuses, do not replace them with fuses of a different type, or other devices that replace normal fuses.
General description of the electrical equipment of the car
The main parts of a 12-volt electrical system with grounded «minus» are 12 volt battery, alternator (driven by crankshaft pulley) and starter.
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. 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, 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.
General recommendations for troubleshooting electrical equipment
Electrical faults are divided into three types:
- An electrical consumer that is not working is not provided with current.
- The user is not working.
- The consumer is not properly grounded.
Faults of the first category are the most difficult. This is the current supply system that contains all switches, relays, fuses, etc.
The electrical circuit can be checked with a test lamp with detachable wires at the other end, on which there are clamps of the type «crocodile».
If the lamp does not work, then follow a systematic approach to determine which of the three causes is manifested:
- Turn on the switch that connects the non-working lamp.
- Disconnect the wire supplying voltage from the lamp.
- Join «earthy» test lamp wire to a good metal ground.
- Touch the test lead of the control lamp to the end of the wire that supplies voltage, which was disconnected from the lamp. If current is supplied to the lamp, the control lamp will light up.
Caution: If the lamp only turns on when the ground is turned on, make sure the ignition key is turned to the «included».
If the test lamp does not light, then there is a malfunction in the circuit between the battery and the lamp. As noted above, this includes all switches, fuses, relays, etc. Find this lamp on the electrical circuit diagram and see how the voltage approaches it. The fault is an open circuit between the battery and the lamp. If the fuse blows and immediately blows again when replaced, this means a short circuit in the circuit, which must be found and eliminated. If the system has a switch, bypass it (short into position «included») using the auxiliary wire by connecting it to the wire coming out of the switch. If the control lamp at the same time lights up, the switch is faulty.
Attention: Never replace the auxiliary wire with a light bulb, as it requires current from the battery.
If the control lamp is off, then current is supplied to the lamp, i.e. the first possible cause is ruled out. Connect the wire supplying voltage and connect the ground wire on the car body with the ground wire on the lamp with the auxiliary wire. In this case, the switch that connects the lamp must be in the position «included» and the ignition is on. If the lamp being tested only works when the ignition is on, then this indicates poor grounding. This is usually caused by the fact that the metal surface on which the lamp is attached is covered with a layer of foreign origin (paint, rust, etc.).
If none of the checks gives a result, then the lamp itself is faulty. The procedure described above can be used for any electrical consumer of the circuit by replacing this non-working consumer with a light bulb. Remember that for reliable operation of the electrical circuit, the connections must be clean and tight.