Strange noise from a/c

[brockdog08]

Good afternoon everyone! I have noticed something going on with my 2005 Explorer that I have never heard before...I have noticed that in the mornings and only in the mornings, when I run my a/c, there is a clear thumping type sound coming from the center dash area from roughly behind the stereo best I can pinpoint. The volume level of it will fluctuate, but not with any function of the truck, like fan speed level or vehicle speed and it comes and goes. If I turn of all the hvac completely, the sound gradually fades and goes away, not abruptly. I have listened for this under the hood, can't hear it under there, just inside the vehicle. Whatever it is does not seem to affect the a/c, it is cool and air flow is good. When I head home after work, there is no noise at all. Anyone have any idea what this could be? I am baffled. Thank you in advance.

 

[spinfisher]

Blend door or control door

may have broken or come loose, I have a 98 so it nay not be the same. You should be able to empty your glove box and pull it forward to get a veiw of what is going on. Good luck, Spin.

 

[brockdog08]

A/C and heat are working good, I can check for this though. What gets me is it only makes noise in the morning, never in the afternoon. This morning, I was in the driveway idling to back out when it started.