Membrane Switch / Ribbon Cable Test; Base Unit Membrane Switch / Ribbon Cable Test - Sub-Zero 700-3 BASE Technical & Service Manual

Troubleshooting Guides

BASE UNIT MEMBRANE SWITCH / RIBBON CABLE TEST

If the integrity of a Base Unit control panel assembly is suspect, continuity tests should be performed at the mem-
brane switch ribbon cable terminal housing. Begin by removing the control panel assembly from the unit and place it
on a solid surface. Disconnect the ribbon cable from control panel PC board.
How To Identify Pin 1 on Terminal Housing
The ribbon cable wires are exposed at the back of the terminal housing, but since there are two vendors of the
membrane switch, determining the location of pin 1 is not always easy. To identify the pins, follow these guidelines:
1. If terminal housing is BLUE, then pin 1 is closest to arrow on housing.
2. If terminal housing is BLACK, check for continuity between first two pins at each end of housing while pushing
Freezer WARMER key. If there is continuity, then pin 1 is at that end.
700BCI-3 Membrane Switch/Ribbon Cable Test Procedure
1. Press no keys on membrane switch. Check for continuity between all pin combinations. With no keys pressed,
there should be no continuity between any pins.
2. Press UNIT ON/OFF key, there should be continuity across pins 3 & 4.
3. Press Door Ajar Alarm ON/OFF key, there should be continuity across pins 2 & 4.
4. Press Freezer WARMER key, there should be continuity across pins 1 & 2.
5. Press Freezer COLDER key, there should be continuity across pins 1 & 5.
6. Press Refrigerator WARMER key, there should be continuity across pins 4 & 5.
7. Press Refrigerator COLDER key, there should be continuity across pins 1 & 3.
NOTE: If any of the tests show failure, replace entire control panel assembly.
Membrane Switch in
Control Panel Assembly
FREEZER
Figure 9-2. 700BCI3 Control Panel Assembly with Cut-Away View to Show Ribbon Cable
#3758424 - Revision B - December, 2005
Integrated
Terminal Housing
NOTE: See "How To Identify Pin 1", above.
COLDER WARMER COLDER WARMER
3
(700- BASE)
ICE
REFRIGERATOR
ON/OFF
ON/OFF
8-18
Series
UNIT
ON/OFF
Ribbon Cable