I have found a chap who supplies replacement switches that turn the light off permanently. you don't even need to strip the seat to replace it. Just cut the wires to the old switch and wire in a matchbox size box unit he supplies.
It comes with all the instructions (really simple-even I could fit it).
All the original (troublesome) switch does- is weigh the passenger. If the passenger weighs less than 40kgs the airbag on passenger side is de-activated. The old switch gives endless problems and are often damaged by children standing on the seat- it is also damaged through routine wear and tear. The stealerships want up to $600 with their labor to replace the part.
If you want to know more email this guy in New Zealand firstname.lastname@example.org
.. He shipped me the part for $65 and I had the light off in 7 days. well worth the wait!!