Sub-Zero UC-24 series Service Manual page 36

Troubleshooting Guides
TROUBLESHOOTING GUIDES
This section of the manual contains:
• The Error Code Table and the Error Code Troubleshooting Guide.
• The General Troubleshooting Guide, which covers all problems that a UC-24 Series unit may experience.
• The Membrane Switch/Ribbon Cable Test Procedures, used to determine if a control panel assembly is defective.
HOW TO USE THE ERROR CODE TROUBLESHOOTING GUIDE
Error Codes indicate problems registered by specific components. If error codes are registered, they will appear
before temperature readings while in Diagnostic Mode.
NOTE: If Error Codes appear with a flashing "SERVICE" annunciator prior to initiating Diagnostic Mode, the unit
experienced excessive compressor run condition that may or may not be associated with the Error Codes displayed.
To initiate Diagnostic Mode, press and hold either COLDER key, then press the POWER key, then release both
keys. Now, check to see if Error Codes are present, being sure to toggle through all error and temperature readings
by pressing either COLDER key or either WARMER key. (See Error Code Table Below)
If Error Codes appear during Diagnostic Mode, follow the Error Code Troubleshooting Guide on the following page.
The left column of the troubleshooting guide lists the error codes. The information in the right column explains what
tests to perform and/or what action to take to correct the error.
NOTE: If error codes are observed in diagnostic mode, a non-flashing SERVICE annunciator will appear on the
LCD when Diagnostic Mode ends, indicating error codes are still stored. Error Codes must be cleared from the elec-
tronic control memory manually. To clear the non-flashing SERVICE annunciator and the error codes, the problem
must be corrected and the unit must be ON, then:
• On a model UC-24C: Press the Freezer WARMER and COLDER keys for fifteen (15) seconds.
• On a model UC-24B, UC-24R, or UC-24RO: Press the Refrigerator WARMER and COLDER keys for fifteen (15)
seconds.
CODE INDICATION
05 Refrig. cabinet thermistor read open or shorted for 10+ seconds, or repeatedly read erratic temp's
06 Refrig. evaporator thermistor read open or shorted for 10+ seconds, or repeatedly read erratic temp's
07 Freezer cabinet thermistor read open or shorted for 10+ seconds, or repeatedly read erratic temp's
08 Freezer evaporator thermistor read open or shorted for 10+ seconds, or repeatedly read erratic temp's
20 Defrost under-heat with no voltage feedback through Gray/White wire at defrost start
21 Defrost overheat
22 No voltage feedback through Gray/White wire at defrost start
23 Defrost overheat with no voltage feedback through Gray/White wire at defrost start
24 Defrost under-heat
30 NA
40 Excessive Freezer Compressor Run
50 Excessive Refrigerator Compressor Run
#7003933 - Revision B - November, 2007
Under Counter (UC-24) Series
Error Code Table
8-2