The led headlights don't light up, all lights don't light up when the switch is turned on, or all lights don't light up in a certain gear after the light switch is turned on. Cause of failure: the power supply line in front of the light switch is open or grounded. The fuse in the line is tripped or blown. The bimetal contact of the light switch is poor or not closed, or the light switch is damaged. After the light switch is turned on, some light wires are grounded, which leads to the disconnection of bimetallic contacts. Fault diagnosis and elimination must first determine the diagnosis scope.

You can probe according to the sequence of light lines to find out the open circuit or short circuit somewhere. Generally, there is dust or oxidation on the headlight reflector. If the luminous emblem of the bulb filament is weak, it is often caused by the looseness or corrosion of the connector connecting the bulb filament, which makes the contact resistance too large. Power short circuit method can be used to quickly determine the fault location.