noise from left fender
 

when i drive my car for sometime, i hear a loud whistling noise coming from the left fender where the gas cap is located. (the weather is hot and the A/C is on).

i have noticed this noise ever since the dealer changed my air condition system.
and when i touch the left fender i find it to be extremely hot!.

could anyone tell me what might be the reason and what is located under the left finder?

thanks a lot