For AC Cooling Units Check Temperature in enclosure / Ambient around enclosure Is there power to the AC unit?  Check for door contact or jumper at logic pins 3-4Internal fan, External fan, Compressor What is the condition of the ambient air? What is the state of the LED? Solid is normal condition Questionnaire for Failure Identification 1. AC unit not working Mains supply connected, Y/N Cabinet door open/ Bridge not set 2. AC unit not cooling Temperature setting too high Oil marks inside the unit found External fan not working 3. Cabinet temperature high Check parameter setting on the PCB, DIP-switch position Internal fan not working Th.-Exp.-valve, capillary tube broken Unit capacity limits exceeded, too high dissipation heat Ambient temperature exceeded maximum permitted temp. Shut down via HP-switch No air T-difference via evaporator Installation of E-components close to the cooled air outlet, i.e. cooled air short cut