Sub-Zero UC-24 series Service Manual page 51

Under Counter (UC-24) Series
CONTROL PANEL MEMBRANE SWITCH / RIBBON CABLE TEST
If integrity of control panel assembly is suspect, perform continuity tests at membrane switch ribbon cable terminal
housing. Begin by removing control panel assembly from unit and place it on solid surface, then disconnecting rib-
bon cable from control panel PC board.
Pin 1 Identification Procedure
The ribbon cable wires are exposed at the back-side of the terminal housing. Place ohm meter leads between 1st
and 2nd pin from each end of the housing while pushing the Freezer WARMER key of a Model UC-24C, or the
Refrigerator WARMER key of a Model UC-24B, UC-24R, or UC-24RO. When continuity is observed, pin 1 is at that
end of the terminal housing.
Continuity Test Procedure
1. Without pressing any of the keys on the membrane switch, check for continuity across all pin combinations. With
no keys pressed, there should be no continuity between any two pins.
2. Identify model number being serviced in left column of table below.
3. Press key listed at top of table.
4. Corresponding numbers to right of model number and below key being pressed are the pin numbers on terminal
housing that should have continuity.
NOTE: If any continuity tests show failure, replace entire control panel assembly.
MODEL
UC-24B
UC-24C
UC-24R
UC-24RO
Control Panel Assembly
FREEZER FREEZER
POWER
WARMER COLDER
KEY
KEY
3 - 4 NA
3 - 4 1 - 2
3 - 4 NA
3 - 4 NA
Figure 9-2. UC-24C Control Panel Assembly
8-17
Troubleshooting Guides
REFRIG REFRIG
WARMER COLDER
KEY KEY KEY
NA 4 - 5 1 - 3
1 - 5 4 - 5 1 - 3
NA 4 - 5 1 - 3
NA 4 - 5 1 - 3
Ribbon Cable Terminal Housing
NOTE: See "How To Identify Pin 1", above.
#7003933 - Revision B - November, 2007