Thermistor Circuit Open Or Shorted —Backup Operating System (Bos); Open Or Shorted Thermistor; Backup Operating System (Bos) - Norcold 121X Series Service Manual

Thermistor Circuit Open or Shorted —Backup Operating System (BOS)

Open or shorted thermistor

This fault is indicated by a blinking
temperature setting. It may be set by:
 Intentionally disconnecting the thermistor
from the circuit.
 An open thermistor (O.L. indication).
 A shorted thermistor (0 resistance).
 Broken thermistor wire leads.
 Corroded or broken thermistor connectors.
The fault causes the temperature setting
number to blink anytime the TEMP SET
switch button is pressed. After ten seconds
the blinking setting turns off.
Check thermistor wires at thermistor and
at connector. See Figure 3-9, page 19.
2
Wires and connections in clean and
in good condition?
YES
Measure thermistor resistance. See
Figure 3-10, page 19. Refer to page 19
Table: Thermistor Resistance Values.
18
S 3
ection
1 COLD-
9 COLDEST
Temperature setting flashing?
YES
NO
Blinking
on
SET TEMP

Backup operating system (BOS)

BOS is a duty cycle designed to maintain
cooling anytime the thermistor is sensed
open or shorted.
When the refrigerator is operating in BOS,
changing the temperature setting on the
display increases the cooling cycle. For
example, changing the setting from 5 to 6
increases cooling cycle time. Lowering the
setting from 5 to 4 decreases cooling cycle
time.
Begin
1
NO
Clean and repair connections as needed.
MODE ON/OFF
Thermistor operating as designed.