Air Bag On-off Switch problems of the 1999 Ford F-150

I purchased a 1999 Ford f150 from kings auto mall near cincinnati. The trucks air bag light was on and I did not know what this meant until after I purchased the truck. I had it in the dealers shop to fix the a/c and have other items looked at. They stated that the air bag light was caused by a faulty air bag switch. This is the switch that turns off the air bag when small children are riding in the passenger seat. The dealership had placed a sticker on the passenger window stating that the truck had been safety checked. But yet I purchased a truck that could have killed my 4 year old if the air bag had went off. The dealership stated that they will only pay for half of the repair for fixing the switch. I don't understand how they could have sold me a truck that had this major issue.

While driving about 50 mph and switching lane to left tried to avoid a vehicle in front, hit hard wall on side. Upon impact, air bags did not deploy, and air bag light came on and remained on.

While driving about 50 mph switched lane to left and tried to avoid a vehicle in front, hit a wall very hard on side. Air bags did not deploy, but air bag light had been on for long time.

While driving, driver's side/ assenger's side airbags deployed unexpectedly . In addition, passenger's side airbag deployed with the manufacturer's installed on/off switch turned in the off position. Dealer will not repair the vehicle. Manufacturer has been notified.