- An electrical consumer that is not working is not supplied with current.
- The consumer himself does not work.
- The consumer is poorly grounded.
The first category of faults are the most complex. This is the power supply system that contains all the switches, relays, fuses, etc.
The electrical circuit can be checked with a test light with detachable wires on the other end that have alligator clips on them.
If the lamp does not work, follow a systematic approach to determine which of three causes is at play:
Turn on the switch that connects the non-working lamp.
Disconnect the power supply wire from the lamp.
Connect the test lamp's ground wire to a good metal ground.
Touch the test lead of the test lamp to the end of the power supply wire that was disconnected from the lamp. 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 indicator 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 follow the voltage approaching it. The fault is an open circuit between the battery and the lamp. If a fuse has blown and when replaced it immediately blows again, this means there is a short circuit in the circuit that must be found and eliminated. 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 control lamp lights up, the switch is faulty
Caution: Never replace the auxiliary wire with a light bulb, as it requires current from the battery.
If the control lamp does not light, then current is supplied to the lamp, i.e. 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 layer of foreign origin (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 reliable operation of the electrical circuit, the connection points must be clean and tight.