Video tutorial on how to test a light bulb using a multimeter. A light bulb cannot always be visually inspected to determine if it needs to be replaced. You can also swap one bulb with the other to determine if it needs to be replaced as well, but sometimes you may not have that option. This particular tutorial was done on a 12v application and can be done both on incandescent and halogen bulbs. When testing halogen bulb, make sure you do not touch the lens. The oil from your skin can cause a hot spot in the lens if the bulb is still good and this will shorten it's life span. If you do touch it, clean the bulb with rubbing alcohol. Some bulb designs may vary, especially if they have more than one filament, please refer to a wiring or bulb model diagram to determine what each pin connects to.