FROZEN LETTUCEA topic that came up a while back on the RV America website is frozen lettuce.   This phenomena occurs because the RV refrigerators we use have no real circulation fan in them.   Cold air sinks to the bottom of the box and warmer air stays at the top.   Camping World sells a small fan that runs on two D cell batteries, but this fan doesn't really move much air.   Acting on a tip from a friend, I wired a 12 volt blower into the refer box.   (see pic attached) This fan draws only .18 amps and cost me under $5 at Radio Shack.   The fan is not a muffin fan, but instead has a blower type exit.  That way you can attach it to the refer wall and not cut off the intake.   Mine if fastened with earthquake putty.   My friends is fastened with screws.   I wired it into the light switch circuit, ahead of the switch so it doesn't go off when the door is closed.   It really moves a lot of air and keeps the refer much more uniform in temperature.   In addition, it appears to reduce the need for defrosting frequently.
Here is a picture of my installation:
To defrost our refer, we simply turn it off and go to breakfast.   By the
time we get back, the refer is defrosted.   To defrost the freezer, we
turn the box off, put all the frozen food in the refrigerator side and
go to breakfast, leaving the freezer door open.   When we return, it is
done.   We leave a towel in the bottom of the freezer to capture water
that trickles to the bottom of the box - this is VERY important so that water does not trickle over the front edge and drip into the bottom compartment below the refrigerator is located, which could cause costly damage to the ECC Module, power transfer switches and other electronic components.