When replacing a bulb, inspect the bulb socket. If the socket is rusty or corroded, the socket or light assembly base should be replaced. Also, inspect the lens and gasket for damage when the lens is removed and replace any damaged part.
There are several types of construction designs for exterior lights: those in which the lens is removed and the bulb is removed from the front, those in which the light assembly must be removed as a unit, and LED lighting units. Removing the lens from the assembly of some types could cause damage, and wiping the reflector surface to clean it can reduce brightness. Never attempt to remove the lens from the type in which the socket and bulb are removed from the back of the assembly.
Bulbs are retained in their sockets in a number of ways. Some bulbs are simply pushed into and pulled out of their sockets, and some are screwed in and out. To release a bayonet-style bulb from its socket, the bulb is pressed in and turned counterclockwise. The blade mount style is removed by pulling the bulb off the mounting tab, then turning the bulb and removing it from the retaining pin. LED lighting units are replaced as units when tested to be defective.