Checking lamp switches and electric motors
1. Remove the corresponding switch.
2. Simple switches have only 2 cable contacts. In this case, one contact must always be energized (+), and after switching on, to another contact too. There are also switches with multiple contacts. For these switches, determine from the diagram to which terminal the voltage should be applied, if necessary, first switch on the ignition.
3. Check with an indicator whether voltage is applied to the switch. If the indicator lamp is on, turn on the switch and check if there is voltage at the output terminal. If there is voltage, then the switch is working.
4. If there is no voltage at the input terminal, there is an open in the wiring. The wires should be checked according to the diagram, if necessary, lay a new wire.
Checking the switches-sensors
Sensor switches include, for example, an oil pressure sensor, brake and coolant level sensors.
1. Connect an indicator or an ohmmeter to the input and output wires of the sensor, to do this, disconnect the cables at the switch.
Attention! Switches screwed into the cylinder block, as a rule, do not have ground terminals, since the switch housing serves as the ground pole.
2. With the switch closed, the indicator should show current flow. An ohmmeter is best suited for testing: With the switch closed, it should show 0 ohms, with the sensor open, infinity ohms.
3. The serviceability of the coolant and brake fluid level sensors can be most quickly checked by disconnecting the wire from the sensor with the ignition on, shorting it to ground, for example, on the cylinder block. If the warning light on the instrument panel comes on, the fault is in the sensor.
4. Special case - oil pressure switch: Contact closed with engine stopped (warning light on), the sensor opens at a certain oil pressure.