RE: 2001 (y) berlingo 1.9d van airbag light on dash
Mine has been on and off for the best part of 6 years and it's all down to the the seat and sensor below, nothing else.
My proble is the wife.
I could end the post right there, I know!
Everytime she drives it she moves the seat to midget leg position. When I put it back the light usually comes on and to get it off, I have to fiddle about with the seat position.
So, firstly, try messing with the seat and making sure it is located properly and no foreign objects are under the seat snagging it.