These include, for example, the engine oil pressure indicator light sensor and the brake fluid level indicator light sensor.
A switch is mainly used to close and open an electrical circuit. There are switches that open the connection to the "ground" (-), and switches that open the connection to the positive potential (+).
Checking lamp switches and electric motors
1. Remove the appropriate switch. Simple switches have only two terminals for connecting the wire. In this case, one terminal should always have (+), and the other terminal has a plus after switching on. There are also switches with several terminals. For these switches, you should find out from the diagram to which terminal the voltage should be supplied. Turn on the ignition first, if necessary.
2. Check the voltage with a test lamp. If the test lamp lights up, turn on the switch and check the voltage at its output terminal. If there is voltage, then we can say with certainty that the switch is working. If there is no voltage at the input terminal, this indicates a break in the supply wire. You need to check the power supply according to the electrical diagram, and if necessary, lay a new wire.
Checking the sensor switches
Sensor switches include, for example, sensors for the brake fluid level warning lights, engine oil level and coolant level.
3. Connect the "ringing" device to the two terminals of the sensor (test light or ohmmeter). To do this, disconnect the wires from the sensor.
Attention! Sensors screwed into the cylinder block, as a rule, do not have a "ground" (-) wire, since their connection to the "ground" (-) occurs through the cylinder block, to which the body of the sensor itself is connected.
When closed (included) the sensor the device should show the passage of current. For such a "ringing" it is best to use an ohmmeter: when the sensor is closed it should show 0 Ohm, and when open - ∞ Ohm (infinite resistance).
At the end of the check, you should check the operation of the corresponding indicator lights on the instrument panel.
4. Disconnect the power wire from the sensor-switch with the ignition on and bring it to the "ground" (-). The indicator light should light up.