Q: heater problems. on 2005 Ford Explorer

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What if you go to turn on the heater and it makes a real loud noise and blows out cold air? when it turned to cold air it does not make the noise. Its like in the flapper that switches it hot to cold.
(1) Answer
The temperature blend door is malfunctioning. It is located inside the dash as part of the heater plenum assembly.

On a 2005 Explorer, things get tricky. Some of these needed only the temperature blend door motor replaced (fairly common across the Ford line of vehicles for years), and a healthy amount also experience cracking in the plenum housing where the motor attaches. In this case, you have to replace the entire plenum box.

The only way to know is to access it and look. This requires dash access/removal. Good luck!
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