Air bag light started coming on /dash constantly

The likely fault is the cables running to the seatbelt pre-tensioners under the drivers or passengers seat in the front of the car.

This may be simply the plug and socket have become seperated from sliding the seat back to clean, a common fault, or the airbag "clockspring" connection unit in the steering wheel has a broken ribbon cable inside the column housing.

To see if its the airbag clockspring, buy a 4 ohm resistor from maplin or radio shack, disconnect the battery on the car, unplug the airbag in the steering wheel and connect the resistor across the 2 contacts in place of the airbag, reconnect the battery, if the light goes out the clockspring is the fault, if not its the SRS system wiring under the seats.