Abstract: In a four wheel drive vehicle wherein unintended engagement of the first driving axle during vehicle use will result in damage to the vehicle drive train, an apparatus for sensing and indicating the status of the front driving axle without requiring the vehicle occupants to stop the vehicle and perform a visual inspection of the vehicle drive train including, in combination, a drive train shaft that rotates whenever the front driving axle of the vehicle is engaged in four wheel drive and a permanent magnet fixedly secured to the drive train shaft. Magnetically activated relay means, such as a reed switch, are operatively connected to a battery in the vehicle and to an illumination means for switching the illumination means on and off.