These "passive belt or "automatic seat belt" units you will often find on 87 88 and most commonly 89 Saab 900 3 door hatch back models.  This control unit is commonly bad, and causes non functioning passive belts (the automatic shoulder belts) -  Note, this may not be your only problem with the system...  They also tend to bind cables, which causes non operation.  Lube up the cables and replace the control unit, you may get your seat belt function back! 

I will warranty this control unit to function for 30 days after you receive it - if your motors work freely, it should last you for years.  These often fail due to seat belt motors being jammed due to lack of lubrication.