[B and C]

Any ideas on what could cause a humming noise in the upper console cabinet on the passenger side of the cockpit.  There are two circular 2" vent openings in the upper far corners on both sides of the upper front cabinets and there is a hum or fan type noise coming from the right one.  Below is a picture of the back and you can see the vent at the top and a junction box mounted on the outer wall.  I can't get into the area without dismantling the cabinet.  I hear a slight sound change when I turn on the small overhead light in the right side audio cabinet.  Very odd.
Thanks.

[Richard]

There are one or two pancake cooling fans in that area to keep the AV equipment cool. Look for a snap disc thermostat switch that turns them on and off.

[CaptainGizmo]

Betcha gotta cooling fan up there!
It's ashame you can't get to it to check.

If it were me (insert: curiosity kills the cat), and drove me nuts, I'd be doing the following:

Stick camera up there and, if that didn't reach or show anything, I'd be sticking a long and flexible something up there to poke around...LOL

[BusNit]

I need to put a cooling fan in mine. That area exceeds 160º when sitting outside and coach is still air conditioned. Power packs for DVD and soundbar thermally trip off.

[Jack Houpe]

Yes my fan made noise too but I unplugged the thermostatic switch and no more noise no more fan either but I the only electronics I have there now is my camera system, all the sat stuff is gone.

[B and C]

Thanks everyone.  Found the thermostat and now everything is good.  Safe travels.
Thanks again.