Found the Reach-In Cooler unit in the defrost cycle. Was told the unit goes into defrost often and asked if this was normal. Could not answer the question. The unit came out of defrost and cooled down to 37 degrees Fahrenheit and then took its time. Put gauges on the unit and the suction pressure was low at 8 PSI. Added refrigerant to bring the pressure up to between 15 and 20 psi.. The unit cooled down to 34 degrees Fahrenheit and then came back on at 40 degrees Fahrenheit. Moved the set points to come on at 37 degrees Fahrenheit and off at 33.5. Found a piece of paper blocking some air flow in the evaporator. The unit went into defrost again so I called technical service and talked to Becky. She said the unit will go into defrost every hour and say defrost for about twenty minutes an hour. Leak tested briefly but did not find a leak. If the unit losses its refrigerant again a more the leak will have to be found and fixed. The unit is up and running.