ive done a search, believe they are the "pre-tensioners"

 

do these need to be connected? how do they work?

 

cant seem to see anything to connect them to & wondered if its ok to just cut em off.

 

not all cars have them?

wild guess....are they the ones that connect to the dash light that lights up red when you haven´t put your belt on ..or is that light totally random, haven´t figured that one out yet as the light goes off if I put the belt on before starting the engine , but stays on a while if I buckle up after i,ve driven a few meters.

Get rid of them. They aren't pre-tensioners, they are the auto-slackeners. Nissan designed in a little widget to always give a little bit of pre-programmed and controlled slack on the belt when the occupants were wearing them. I am sure it was great when the units were new, but as with all seatbelts, they furr up, the mechs bind a little and the whole system ends up jamming. You may have experienced seatbelts that have refused to wind in. That's usually a symptom of that.

 

Mine did it a little bit, even after I spent ages cleaning the seat-belt webbing. My seatbelts recoil quite nicely now, certainly better than almost every Z I've been in. But the slack mech still played up, so I just disconnected it and the belts have been perfect ever since.

 

You are better off unplugging them from inside the door though (if you have a series one) as the system might be live from that point.