Probe lamp (with needle contact)
With its help, you can check the presence of voltage in the circuit. The brighter the lamp burns, the higher the voltage. The needle pierces the insulation of the wire under test. The other terminal on the lamp wire is connected to «mass» (car metal). Attention: the test lamp consumes a lot of power, therefore it is not suitable for testing electronic devices. This requires a voltage probe with LEDs.
Probe with LEDs
Depending on the version, this device indicates the presence of direct and alternating voltage between 6 and 700 V. Visually, the presence of voltage is determined by the lighting of the LED. Simple devices of this type are inexpensive.
Universal tester
This device can measure voltage, current (constant and variable), circuit resistance. Suitable instruments with a digital display are now also inexpensive. The power supply of such a device is usually carried out from a battery.
Voltage measurement
In order to measure the voltage, for example, at the battery terminals, connect the instrument wire with the negative terminal to the negative terminal of the battery or «mass». Connect the positive terminal to the positive terminal of the battery or the wire under test. If the device shows only 10.4 V, this indicates a short circuit in one of the battery cells. It is also necessary to check the battery voltage when starting with a starter - the resulting value of 5 V indicates a battery malfunction.
Current measurement
To do this, you must connect the device directly to the circuit. During a series of measurements, it is sufficient to unplug the plug and connect the wire between the two contacts.
Attention! Always consider the threshold values that your tester can measure. Very high currents flow at the contacts of consumers such as a starter or glow plugs, which can damage the device during measurement.
Resistance measurement
In this case, the tester checks whether the current passes through a particular wire or switch. If the current flows freely, the resistance value will be zero. If there is a break in any place, the resistance value will tend to infinity. In addition, you can find out what internal resistance this or that device has.