Sub-Zero UC-24 series Service Manual page 38

Troubleshooting Guides
ERROR CODE TROUBLESHOOTING GUIDE
EC
20 A. With cold evap. (< 10°F / -12°C), initiate Manual Defrost, then initiate Diagnostic Mode (press POWER key every
20 seconds to keep in Diagnostic Mode) and observe evap. temp. If temperature exceeds 45°F (7°C) and defrost
lasts longer then 5 minutes, error code is false. Clear error code. If error code is not false:
1. Check continuity of Grey/White wire from defrost heater to J2 on control board. Reconnect / repair Grey/White
wire.
2. While in defrost, check for AC power at P2 on control board. If no voltage, replace board.
3. Check continuity of Blue wire from defrost terminator to P2 on control board. Reconnect / repair Blue wire.
4. Check resistance of defrost heater (see wire diagram for proper resistance). Replace heater if defective.
5. Check electrical connections and operation of defrost terminator - Cut-in 30°F (-1°C) /Cut-out 55°F (13°C).
Reconnect / repair or replace terminator.
6. Reference wiring diagram to identify components in same White wire circuit as defrost heater. Check all White
wire electrical connections and continuity from defrost heater to P4 on control board.
21 A. With cold evap. (< 10°F / -12°C), initiate Manual Defrost, then initiate Diagnostic Mode (press POWER key every
20 seconds to keep in Diagnostic Mode) and observe evap. temp. If temperature does not exceed 105°F (40.5°C),
error code is false. Clear error code. If error code is not false:
1. Check Blue wire connection at control board (P2). If connected to wrong pin, connect correctly.
2. Check Grey/White wire connection at control board (J2-3). if connected wrong or bad connection, reconnect /
repair.
3. Check for proper mounting & location of evap. thermistor, defrost heater & terminator. Remount correctly.
4. Check for electrical short of Blue wire to another circuit. Repair Blue wire &/or electrical connections.
5. Check operation of defrost terminator - Cut-in 30°F (-1°C) /Cut-out 55°F (13°C). Replace if defective.
22 A. With cold evap. (< 10°F / -12°C), initiate Manual Defrost. If compressor starts 5 minutes after defrost is initiated,
check Grey/White wire and continuity from defrost heater to J2-3 on control board. Reconnect / repair Grey/White
wire.
23 A. With cold evap. (< 10°F / -12°C), initiate Manual Defrost. If compressor starts 5 minutes after defrost is initiated,
check Grey/White wire connections and continuity from defrost heater to J2-3 on control board. Reconnect / repair
Grey/White wire.
B. Check for proper mounting and location of evap. thermistor, defrost heater & terminator. Remount correctly.
C. Check Blue wire connection at control board (P2). If connected to wrong pin, connect correctly.
D Check for electrical short of Blue wire to another circuit. Repair Blue wire &/or electrical connections.
24 A. With cold evap. (< 10°F / -12°C), initiate Manual Defrost, then initiate Diagnostic Mode (press POWER key every
20 seconds to keep in Diagnostic Mode) and observe evap. temp. If temp. exceeds 45°F, error code is false. Clear
error code. If error code is not false:
1. Check Blue wire connection at control board (P2). If connected to wrong pin, connect correctly.
2. Verify proper location of Grey/White wire at control board (J2-3). if connected wrong or bad connection, recon-
nect / repair.
3. Check for proper mounting & location of evap. thermistor, defrost heater & terminator. Remount correctly.
NOTE: Always clear Error Codes after repairs are complete.
#7003933 - Revision B - November, 2007
Under Counter (UC-24) Series
TEST / ACTION
8-4