Voltage measurement
Pilot lamp: this is a lamp with a needle contact, the needle of which can pierce the insulation of the wire under test. The terminal on the lamp wire is connected to some bare metal place in the car, i.e. to the mass. The lamp first of all signals whether there is voltage. By the brightness of its burning, you can approximately estimate the magnitude of the voltage.
Diode indicator: electronic assemblies cannot be checked with a conventional test lamp. It consumes a lot of current and can thus damage the components of the electronic circuit. To measure in electronic circuits, you need to purchase a voltage indicator with an LED.
Voltmeter: more accurately, the voltage can be measured with a voltmeter with an arrow or a digital display. Measurements with a voltmeter do not harm electronic components.
- To measure battery voltage (as an example) test lead with designation «–» connects to the negative pole of the battery. positive wire (+) set to the positive pole.
- Voltage measurement using ground: connect (+) the positive wire of the meter to the appropriate terminal; negative wire (–) connect to bare metal of body or engine.
- More often voltage is measured between 2 specific pins (e.g. in control panel). How in this case you need to connect the measuring device and measure the voltage, and then compare it with the value, is indicated in the technical documentation for this contact pair.
- With a voltmeter, you can check whether the ground wire is in order: connect the positive wire of the measuring device to the positive pole of the battery, and the negative wire to the end of the ground cable. If «weight» is working, then the device should show the exact voltage of the battery.
Current measurement
Whether electric current flows to the consumer can be measured with an ammeter or tester with the appropriate measuring range. To do this, the electrical circuit must be disconnected and the measuring device connected between the free contacts.
- In practice, this is as follows: disconnect the connecting contact of the wire going to the consumer and connect the measuring device between the plug-in block and the connecting contact.
- The current strength is measured, for example, if there is a suspicion that somewhere there is «secret» current consumer that discharges the battery overnight. To discover a place «leaks», disconnect the ground wire from the battery and fix an ammeter between the battery pole and the ground wire. If the instrument indicates the presence of electric current, the electrical circuit should be determined: remove the fuses one by one and instead connect the ammeter to the contact tabs in the fuse box. In this way, you can determine in which electrical circuit losses occur.
- Using the fuse table presented in the next chapter, you will be able to determine which consumers are included in this electrical circuit and check them one by one.
Resistance measurement
Measuring the resistance in any node using an accurate ohmmeter is advisable only in the following cases:
- The resistance measurement shows, for example, what intrinsic resistance a particular node has.
- Ohmmeter wires (the position of the poles does not matter) for this, they are connected to two terminals of the corresponding node.
- When measuring resistance «masses» one wire is connected to the corresponding node, the second - to the engine block or body.
- Next, it is checked whether the wire or switch has «pass» - then the measurement result is zero, or the course of the electric current is interrupted - then the measurement result tends to infinity.