i have a 93 w250, diesel, the rear axle has a electrical connection on top of the pumpkin over the ring gear, mine is broke,

what is it, can i buy another one, do i need it, the plug in is dangling in mid air and my brake light on the center panel is on,,,,

 

That is for your ABS pick up coil. You can either fix it so the ABS works or take the bulb out and have no rear ABS.

 

you can buy the sensor at your local auto parts store.