Coolant temperature gauge
If the pointer is constantly at the beginning of the scale, then with the ignition on, disconnect the wire from the pointer sensor and connect the tip of the wire to the housing. If the pointer deflects, then the sensor is faulty and it is replaced. If the pointer does not deflect, then remove the combination from the instrument panel and, without disconnecting the wires from the combination, with the ignition on, connect the upper terminal of the temperature gauge to the housing, which is connected to plug "2" (see figure 154) of the right (white) block of the combination. The deviation of the arrow in this case will indicate the serviceability of the devices and a break in the wire connecting the sensor to the combination of devices.
If the pointer is constantly in the red zone, disconnect the wire from the sensor with the ignition on. If the sensor is faulty, the pointer should return to the beginning of the scale. If the pointer remains in the red zone, either the wire has a short circuit with the housing or the device is damaged. The serviceability of the device can be checked by disconnecting the right (white) block of devices from the instrument cluster and connecting plug "5" to the housing and plug "12" of the white block of the instrument cluster to the "+" of the battery. In a serviceable device, with the ignition on, the arrow should be at the beginning of the scale.
Fuel level indicator
The testing method is similar to the one described above. Just keep in mind that the pink wire is connected to the sensor resistor, and the blue wire with a red stripe is connected to the contact that turns on the fuel reserve indicator lamp.
If the pointer of the indicator is constantly at the beginning of the scale and does not deviate after the pink wire tip, disconnected from the sensor, is connected to the body, then the device is checked. To do this, remove the instrument cluster and, with the ignition on, connect the lower terminal of the indicator to the body, which is connected to the plug "13" (see figure 154) right wiring harness (without disconnecting it from the instrument cluster). In a working device, the arrow should move to the end of the scale.
If the pointer is constantly opposite the "1" mark, the serviceability of the device can be checked by disconnecting the right (white) block of wires from the instrument cluster and connecting the "5" plug to the housing and the "12" plug of the white block of the instrument cluster to the "+" of the battery. In this case, the arrow of a serviceable device with the ignition on should be opposite the "O" mark.
[The original source is published on the website VazBook.ru]