Sanyo 1206 Cooling Problem

[TerryM]

My Sanyo has been working great with 1/4 barrels since I got it over a year ago, keeping the brew at 38-degrees with the dial indicator at the 3:00 position. Last week I got a 1/2 barrrel of Heineken for the upcoming holiday weekend, and increased the temperature control dial to max (about the 5:30 position), but cannot get the temperature under 40-degrees.

I monitor the temperature with a food testing thermometer stuck into a sealed mini-tupperware container filled with water. I checked the calibration with ice water, so the temperature reading is accurate.

The cooling plate is ice free except for a little ice formed at the lower right quadrant of the section along the back of the fridge.

No modifications have been made to the fridge. The door seals all seem to be okay.

Any ideas on what is happening / what I can do to get some 38-degree Heinie for the holiday? (I know, I know ... Option 1 is having the wife sit on a block of ice.)

If the ice on the cooling plate is the culprit, how should I get rid of it without shutting the fridge down and warming up the the beer?

Thanks.

TerryM