Checking lamp switches and electric motors
1. Remove the corresponding switch.
2. Simple switches have only 2 contacts for cables. In this case, voltage (+) should always be applied to one contact, and after switching on, to the other contact as well. There are also switches with several contacts. For these switches, determine from the diagram to which terminal voltage should be applied, if necessary, first switch on the ignition.
3. Check with the indicator whether voltage is applied to the switch. If the indicator lamp is on, turn on the switch and check whether there is voltage at the output terminal. If there is voltage, then the switch is working properly.
4. If there is no voltage at the input terminal, there is a break in the wiring. The wires should be checked according to the diagram, if necessary, lay a new wire.
Checking switches-sensors
Switches and sensors include, for example, an oil pressure sensor, brake fluid level sensors and coolant level sensors.
[The original article is posted on mazbook]
1. Connect the indicator or ohmmeter to the input and output wires of the sensor, to do this, disconnect the cables on 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. When the switch is closed, the indicator should show current flow. An ohmmeter is best suited for checking: When the switch is closed, it should show 0 Ohms, when the sensor is open, infinity Ohms.
3. The fastest way to check the coolant and brake fluid level sensors is to disconnect the wire from the sensor with the ignition on and short it to ground, for example, on the cylinder block. If the warning light on the instrument panel lights up, the fault is in the sensor.
4. Special case - oil pressure sensor: When the engine is not running, the contact is closed (the signal lamp is on), the sensor opens at a certain oil pressure.