- 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 a power supply system that contains all switches, fuse relays, 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 has manifested itself:
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 end of the test lamp to the end of the wire supplying voltage that 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 malfunction is an open circuit between the battery and the pump. 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 there is a switch in the system, bypass it (short into position «included») using an auxiliary wire, connecting it to the wire coming out of the switch. If the control lamp lights up at the same time, the switch is faulty.
WARNING: Never replace the auxiliary wire with a bulb, as it requires current from the battery.
If the control light is off, then current is supplied to the pump, 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 connecting the pump 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 pampa 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.