I have an 02 Ranger that the air bag light will come on. The senerio is that the vehical must be cool, not driven any real distance (30 minutes or less) in a day or more, light rain(or heavy)increasing the humidity level regardless of tempature (interior sticky to the touch)and the airbag light will come on. Run the truck 20 minutes or more with A\C compressor running (defrost or A/C, air warm or cold) and dry the cab (not sticky to the touch) and restart the engine light goes out. I thought I had heard of an issue with the seat connectors?? Note: No water is getting in the cab and it is not effected by running in the rain.

 

my 03 did something similar, I simply changed the air bag switch out, it's below the ashtray and I've not seen the light since.

 

I talked w/ my ford mechanic. It is a semi known issue that the passenger seat connector comes loose and will start to corrode. He said to pull the connector and pack w/dielectric grease.