I have a 98 f150 4x4 V 6. When I turn on the AC it blows cool for a sec then blows warm. I turn on the heat and it blows warm for a sec then no heat. Any ideas out there? I just bought the truck so I can't answer any maint. Questions. It had a clean carfax if that means anything. Thanks in advance. Email @ johnschmenk@yahoo.com