2004 Explorer "banging noise"

[jsgold]

When I start up the 2004 Explorer I got from my son recently it will make a single loud "bang" noise a few seconds after startup. No noise after that at all. Been trying to figure it out and it seems it has to do with a/c kicking on. I never hear the noise in the morning, always later in the day. Does it sound like perhaps a vent door sticking perhaps???

[shorod]

Do you hear the noise outside the truck, or only inside? You refer to it as "loud" but do you just mean audible, or would it startle most people if they were not expecting it? Might it be described more as a "pop" or "click"?

-Rod