1998 Cherokee. Driving down the road, the air bag light will come on and speedometer and tach will drop to zero at same time. Then they will start to work again on there own. Any ideas where to start looking would be appreciated.

 

You either have loose or dirty connections on the back of the instrument cluster. Next time it happens slap the dash above the cluster and see if they come back on. You will need to pull the cluster and clean all of the connection and make sure that they are all tight when you put it back together.