I have a problem with the Air Blower. As soon as I start the car, there is air blowing in full speed from all the vents in the front (haven't checked back), even when the A/C is switched off and the fan is in off position. Any idea why? and what to check?

 

the center console/rear vent is just a plastic tube that feeds off the main line
Keep its vents open to reduce pressure (air/temp leaks into center console and CD's etc)and let the moving out the back and towards to cabin venting

manual fan control- non navi car?
switch would be my first guess
Have you pulled the cabin filter and looked at the blower motor wiring and resistor- potential probs in there