wierd problem just occured on my 2003 g35 sedan....just happened this past few days its goes on and off. So its pretty much 28+ degrees lately here in toronto and the knocking sound occurs only when its really hot and ac fan its on ful blast but at night it doesnt but still have my ac full blast.

The sound is right in the front passenger underneath the dash where the fan is


So im a bit confused on the situation on how to resolve this issue, anyone else had the problem and the fix for it???