The first step should always be to check the fuse protecting the relevant electrical circuit.
If necessary, replace the blown fuse, and after turning on the consumer, check whether the fuse blows again. In case of burnout, it is necessary to find out the cause and eliminate it. As a rule, this cause is a short circuit, i.e., in the connections or inside the consumer itself there is a connection of the parts of the supply voltage circuit to the ground.
Electrical faults are divided into three types:
- The electrical consumer does not work because it is not supplied with current.
- The consumer himself does not work.
- The consumer is poorly grounded.
(The article was copied from here: «NISSANBOOK.RU»)
Faults of the first category are the most complex. This is the power supply system that contains all the switches, relays, fuses, etc. The electrical circuit can be tested with a test light with wires ending in alligator clips.
If the lamp does not work, to determine which of the three causes is at play, you need to follow a systematic approach:
- Turn on the switch that connects the non-working lamp.
- Disconnect the wire supplying voltage to the lamp.
- Connect the negative wire of the test lamp to a good metal ground.
- Touch the test lead of the test lamp to the end of the wire that supplies voltage to the lamp and is disconnected from it. If current is supplied to the lamp, the control lamp will light.
Caution: If the lamp only comes on when the ground is turned on, make sure the ignition key is turned to the "on" position.
If the control lamp does not light, then there is a fault 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 diagram and trace how the voltage goes to it. The fault lies in the break in the circuit between the battery and the pump. If a fuse blows and immediately blows again when replaced, this indicates a short circuit in the circuit that must be found and repaired. If the system has a switch, bypass it (short-circuit it to the "on" position) using an auxiliary wire, connecting it to the wire coming out of the switch. If the indicator lamp lights up, the switch is faulty.
Caution: Never replace the auxiliary wire with a light bulb, as it requires battery power.
- If the control lamp does not light, but current is supplied to the lamp, then the first of the possible causes is excluded. Connect the power supply wire and connect the auxiliary wire from the ground on the car body to the ground on the lamp. In this case, the switch connecting the lamp must be in the "on" position and the ignition must be on. If the lamp being tested only works when the ignition is on, this indicates poor grounding. This is usually caused by the metal surface on which the lamp is mounted becoming coated with a foreign substance (paint, rust, etc.).
- If none of the tests yielded any results, then the lamp itself is faulty. The above procedure can be used for any electrical consumer in the circuit by replacing that non-working consumer with a light bulb. Remember that for the electrical circuit to work reliably, the connections must be clean and tight.