why does heater blow cold air after it was blowing hot air

thanks I will check those things out. where do I begin to look for temp door actuator?

Are you sure it's a 99, doesn't show a 2.3L since '92. Then it should be a cable going to the top of the heater box.

thanks where do I begin to look is it behind glovebox?

you should be able to see it from under the dash but it easier if you take the glove box out