A method and system for detecting the presence of a carrier mounted on the rear of a motor vehicle or of an object carried by the carrier that may cause damage or a malfunction of a rear wiper system of the motor vehicle. If a potentially obstructing situation is determined to be present, the rear wiper system is deactivated to prevent it malfunctioning or being damaged by the obstruction. A user of the vehicle may be provided with a message that an obstruction has been detected and the user may control whether the wiper system is deactivated. The obstruction may be sensed by monitoring the amount of current drawn by a wiper motor, by an ultrasonic sensor, or by a rear-view camera.