Clifford Solaris Problem

I was moving some wires in the engine compartment, specificially those that run to the back of my siren.  When I moved some of the wires one of them broke off from inside the tape.  I took it apart with the intent to reconnect the wire to the end that broke off.  The wire is the ground wire coming off of the siren, it had 2 butt connectors connecting what I *think* is some sort of diode.  Its broken and I am able to read what I beleive is U28 on it.  Its a small round black tube.  Not sure exactly what it is but im going to guess its a diode.  The follow pictures are of it attached to the butt connector.  Tried to get as close as possible.

http://www.rickone.com/rob/diode1.jpg

Rob