Some refers take forever and a day (OK, I'n exaggerating, more like overnight) to properly cool down.
If that's not your issue, investigate adding small computer fans.
Some people get good results putting a couple of them inside the refer, and that just moving around the air makes a good difference.
Others find that installing some on the back to move air over the left to right fins you see, neat the top of the back on most refers.
Google this idea, or here
is a look at what I am talking about.