A trailer lighting activation system includes a vehicle light sensor, an ambient light sensor, and a microcontroller. The vehicle light sensor is removably attached to a towing vehicle light to detect a light output of the towing vehicle light, and to provide a vehicle light sensor output signal in response to the light output of the towing vehicle light. The ambient light sensor can detect an ambient light level and provide an output signal in response to the ambient light level. The microcontroller is coupled to the vehicle light sensor output and to the ambient light sensor and has an output for energizing a trailer light in response to the ambient light sensor output signal and the vehicle light sensor output signal. An overcurrent monitor is coupled to the trailer light and to monitor current drawn by the trailer lighting activation system.