When I turn the dial to medium it blows cold but heat works only on high.

 

Since the blend doors are electric, I think the first thing I would check is coolant level and thermostat for being open. On second thought, could there be dirt or anything in the temp switch itself? Does it feel normal to turn it? My 2 cents. Good luck.

 

my problem was when i stop the car and turn off open the driver door the blower would come on

 

That sounds like the cooling fan in the engine compartment ...normal behavior.

 

it blows from the dash and lights up

 

Mis-post, my bad!