Possibly a fan, but parts diagrams can be checked to confirm what's back there if you provide the specific brand and model number of your unit.

It's a Kitchenaid French door. I did find a parts diagram online, though it was for a previous model. The part is listed as a "control" but to what, I'm not sure. It might possibly be a damper ...? There is also a part called "insulation" inside there, then the cover, and it looks like that's it. Would a "control" have any moving parts on it that would cause it to vibrate and rattle?

This post was edited by jellytoast on Wed, Jun 26, 13 at 16:48

There's a gerbil in there on a wheel - that's what makes the refrigerator work :-)

You don't say how old the refrigerator is but they used to put the defrost timer in that area. It has a motor, gears, etc. and can make the noise you're describing

weissman, you don't know how badly I want that to be true.

jakvis, the refrigerator is brand new.

I called and there was an opening for a service guy to come out tomorrow, so they mystery will be solvedI'll make sure he gives the gerbil a treat while he's in there greasing the wheel.

It's 2018 and I am having the same issue. What was the resolution to the noise?

I had rattling with a new LG. After much difficulty with the "service" people at the local big appliance dealer, it was resolved by an LG authorized service provider (not the outfit I bought the fridge from). As I discovered on the LG website (not to be believed by local dealer) it was caused by improper installation - both the leveling of the fridge and the installation of the door. Dealer's "service" people scratched the door when they improperly installed it and had to install a new door (which they did incorrectly). The authorized service provider corrected the problems resulting from the others' incompetence.