1999 Dodge Van INLINE CHECK VALVE

DIRECTIONAL SWITCH DOESN'T WORK ON MY RAM VAN 1500. I TURN AIR ON TO BLOW THRU DASH AND IT BLOWS FROM DASH AND THEN I STILL HEAR THE FAN, BUT THE DIRECTION IS NOW ON MY FEET OR WINDSHIELD. I WAS GOING TO REPLACE THE ENTIRE 3-SWITCH CONTROLS ON DASH, BUT DODGE PARTS DEPT TOLD ME IT'S PROBABLY THE INLINE CHECK VALVE. THEY SELL A LOT OF THEM. I BOUGHT THE PART, BUT DON;T KNOW WHERE IT'S LOCATED. ONE SITE SAID IT WAS UNDER HOOD NEXT TO TRANS. FLUID STICK AT THE "T", BUT I DON;T KNOW WHAT THAT LOOKS LIKE. PLEASE HELP. WOULD BE GREAT IF YOU HAD A DIAGRAM OR A VIDEO.