Hot Air problem and tapping noise

98 Ranger XLT 4cyl. Auto, bought new, always maintained on schedule.I still use 5-30 oil (synthetic),and don,t leak or burn a drop of oil. I have 70,000 miles on it and never had a problem.Now I have problem many seem to have.Heat coming out at all settings.Tried recomended free fix, (excellent problem solver) but found nothing was busted at the box.Could it be flap inside is busted? Also, when I start engine it runs strong and quiet.When I put it in gear I get a tapping noise that sounds like a valve tap.Any suggestions.
Thanks