SCSI termination problems are difficult to diagnose. Besides the suggestions
below, there are a number of other articles that may be of help by searching
under "SCSI" and "termination".
1) Make sure the external drive is turned on before the Macintosh is.
2) Make sure the SCSI ID on the external drive is not set to zero. It should
be between 1 and 6.
3) Try the 160MB drive on another machine, preferably without an internal
hard disk. If it has problems it could be the cable or the hard disk.
4) Swap the cable and the terminator if neccesary.