Typically, the main function of a switch is to close and open the current supply circuit. There are switches that open the ground connection and switches that open the positive voltage supply circuit.
Checking lamp switches and electric motors
Remove the corresponding switch.
A simple switch has two contacts for wires. In this case, voltage is supplied to one of the contacts constantly, and to the other - when the switch is triggered. There are also switches with several contacts. For such switches, you need to find out from the electrical equipment diagram to which contacts voltage is supplied, if necessary, turning on the ignition.
Using a test lamp, check whether voltage is supplied to the switch. If the test lamp lights up, turn on the switch and check whether there is voltage at the output contact. If this happens, the switch is working properly.
If there is no voltage at the input contact, there is a break in the voltage supply circuit. Check the voltage supply according to the electrical equipment diagram and, if necessary, lay a new wire.
[For details, see the website: www.mazbook.ru]
Checking the sensor switches
To the sensors-switches (control switches) these include, for example, the following: oil pressure indicator light switch, brake fluid and coolant level indicator light switches.
Connect the ohmmeter to the switch contacts, for which you need to remove the wires from them.
Note: The switch that is screwed into the cylinder block usually does not have a ground wire, since the switch housing serves in this capacity, connected to the ground through the cylinder block.
When the switch is closed, the ohmmeter should show 0 Ohms; when open, infinity.
The operability of the coolant and brake fluid level indicator switches is checked very quickly. To do this, with the ignition on, remove the wire from the switch and attach it to a good ground. If the indicator lamp on the instrument panel lights up, the switch is faulty.
The oil pressure warning light switch works differently: when the engine is not running, its contacts are closed (the control lamp is on), and when a certain oil pressure is reached, the switch opens.