To check, you must use the tester in resistance measurement mode.
Disconnect the electrical connectors from the switch and measure the condition (closed or open) electrical circuits between the contacts that must correspond to those shown in the figure.
Measure at all switch positions.
Check the condition of the switch and relay contacts. If the contacts are oxidized, clean them.
If the electrical circuits are not in the correct condition, replace the switch.
Check the resistance of the headlight range control switch between the terminals with the switch operating.