i have a 1997 f150 the air works great but the temp doesnt get warm AT ALL when i turn the ****...some friends said to check vacuum hose but i dont have a clue which one or where it would be...also when im driving and my overdrive kicks in it blows from my vents to my defrost....please help!!!!! im so lost

 

Not really an electrical issue, might be sparse answers.

Try a search for blend door, this shows the vacuum lines specific to the blend door.

Might also want to check the vacuum lines behind the HVAC control panel, to make sure none of them are cracked.