On an 86 there shouldn't be any seatbelt buckle switches for the airbag. Starting in 1988 there would be a pair of seatbelt buckle switches for the airbag and a seperate one in the drivers buckle for the seatbelt warning light. Possibly you have a newer owners manual?
In any event, on your car the most common cause for trouble is the contacts in the upper steering jacket for the airbag. They are sort of like the contacts for the horn, and they wear out like brushes in an electric motor.