A ballast resistor is used to regulate the voltage in a single filament bulb used in a dual filament headlight. If one of your headlights is out, it could be due to a bad ballast resistor. Leave it to GarageMatch experts to diagnose and fix this issue. Submit a service request today and we'll connect you with qualified repair shops to handle your unique needs. It's important to note that GarageMatch is not a repair shop, but rather a service that connects users with repair shops that cater to all makes and models of vehicles. Do you have any further questions about ballast resistor replacement? [Note: This description may be truncated.]