Arrived at job and customer informed tech that the call was actually for his house. Customer gave tech address and tech drove to house. Unit is reach in refrigerator and is freezing product. Tech turned unit on and watched it pull down to 30. While it was pulling down tech leak searched unit, found no leaks. Once unit had pulled down tech adjusted temp controller to make sure unit was responsive to control. Called customer and he said that the person he got unit from said it would run fine for a few hours then if it would just run without stopping causing everything to freeze. A previous company had diagnosed unit with a bad temp control before the customer got the reach in. Tech will submit parts order sheet to have new temp control ordered.