Ford Taurus X 2008 everytime I turn the heat off it clicks up under the dashboard when I turn the blower on it doesn't defrost my windshield I give off eat

its the blend door making the selection of which to use the ac or the heat

There may be something in the blower motor, that has either fallen into the defrost duct, or your fan may be going out. Remove the cab filter or remove the fan cover and investigate.

it is a common problem caused by the sun

If both heater hoses are hot, the problem could be a stuck or faulty blend door under the dash.
The blend doors direct air thru the heater core and out the vents.

You have a loss of vacuum from the engine, first check under the hood and make sure the vacuum storage tank is not damaged and leaking and it has vacuum in it when the engine is running. If all that is ok then move on to the line that goes inside the truck and verify it has vacuum.

I have the same car and just fixed the exact same problem you just described.
It is NOT a vacuum problem. The blend door is electronically controlled my a small motor under the dash, to the right of the steering column. The clicking is coming from a stripped gear in that small motor unit.
On my Taurus X, what caused the motor to fail was the blend doors (which open and close depending on what your vent setting is on) getting stuck. That caused the motor gears to strip out and make a clicking sound every time the automatic climate control tried to move the blend doors.
The fix required a substantial amount of the dashboard to be taken apart. The blend doors were re adjusted and the motor control unit replaced.
I had the Ford dealership do the repair and it cost me $450. (Ouch!)
To make sure that's your problem, you can follow the clicking sound. You'll have to get on your back and look under the dash on the drivers side. Have somebody press the defrost button to cause the clicking sound. Once you find the small unit you can actually feel the gears slipping when it makes the clicking sound. It's really tight under there though and you'll probably need a flashlight.

Jeremy is right but it will be a lot easier it you remove the glovebox door and inner pocket to get to the plug for the blower motor

Good Luck!

Make sure you have the heat selection set all the way to heat. In Ford and Dodge vehicles, when you select Defrost the AC compressor actually kicks in and if you have the temperature selection set to the cool side it will push cold air to defrost your windshield.

get it down to the gararge to get checked out !!!!

probably a bad blower motor. check for rust corrosion inside from water dripping on it from air intake at base of windshield under screen.