If the lamp is normal, do the following: connect two wires to the positive terminals (contacts) of the battery, and connect their other ends to the lamp contact. It does not matter how the wires are connected on the lamp. One wire is connected to the lamp body, and the other to its contact. If the lamp does not light, replace it.
Note: Make sure that the contacts on the lamp and in its socket are not corroded. Clean the contacts if necessary.
If the lamp is in good condition, then insert it into place and turn it on. If the lamp does not light, then check the voltage supply using a test lamp. To do this, one wire of the test lamp must be applied to a good ground or directly to the negative terminal of the battery. The other wire of the test lamp must be connected to the voltage supply plug or to the wire. If the test lamp lights up, but the main lamp still does not light, then the connection of the lamp to the "ground" is faulty. To check this, apply the "ground" wire to the lamp socket. It should light up.
Note: Some lamps have only one contact for voltage supply (for example, for parking or interior lighting). Such lamps are connected to the "ground" directly through their housing.
If there is no voltage on the wire going to the lamp, i.e. the control lamp does not light, then most likely the switch is faulty. Check for contact in the switch.
For details, see the website www.MAZbook.ru