Control lamp (with needle contact). With its help you will check whether there is voltage in the electric circuit: the brighter the lamp glows, the higher the voltage. Simply pierce the insulation of the wire being tested with the needle contact of the lamp. Attach the clamp on the lamp wire to the ground (for example, to terminal 31 (minus pole) of the battery, the engine housing, uninsulated metal of the car body, etc.). Be careful: the test lamp consumes a lot of power and is therefore not suitable for measurements in electronic units (for example, in the engine control unit). In this case, you should use a voltage indicator with LEDs. Voltage indicator with LEDs. Depending on the model, the device induces direct or alternating voltage from 6 to 700 V approximately. Voltage is indicated optically via LEDs.
Multimeter (universal device). They measure voltage, current (direct and alternating) and resistance. Devices with digital indication are better. The power supply of the multimeter is usually carried out from an internal battery.
Voltage measurement. In order to measure, for example, the battery's resting voltage with a multimeter, you must connect the black wire marked with a "-" sign to terminal 31 of the battery (minus pole) or to ground. The red "+" wire of the measuring device is connected to terminal 30 of the battery (positive pole) or to the measured wire. If the device shows only about 10.4 V, this indicates a defective battery cell. Check the battery's functionality when the starter is activated - a measurement result of 5 V (±0.5 V) means that the battery is not in order.
Current measurement: to do this, you need to open the electrical circuit and connect the measuring device to it. As a rule, it is enough if you disconnect the corresponding plug contact in your Focus and then simply connect the measuring device between the connector and the contact tongue. Be careful: always remember the measurement range of your multimeter. Very high currents flow in such consumers as, for example, the starter - your device may suffer from them.
Resistance measurement: a multimeter can be used to check whether there is conductivity in a wire or switch. If the current flows freely, the device will show a resistance value of 0. If there is a defect in the wire or switch, the measured resistance value will be equal to infinity (∞). In addition, you can use a multimeter to measure the internal resistance of electrical components.
Schematic connection of the multimeter: Current (A), voltage (V) and resistance (Ohm). Consumers are, for example, lamps, electric motors or a starter.