Control Diagnostic Function (Models N620, N621, N820, And N821) - Norcold N620 Service Manual

Control Diagnostic Function
(models N620, N621, N820, and N821)
The Control Diagnostic Function allows the repair technician
to put the refrigerator control into a diagnostic display mode.
This mode provides the repair technician with specific
diagnostic information which can be helpful when trouble-
shooting refrigerator control problems.
The diagnostic display mode consists of eight different
display screens. While each of these screens show different
information, they all use the individual segments of the 7-
segment display. The individual segments are:
s e g m e n t 2
s e g m e n t 5
To put the refrigerator control into the diagnostic display
mode, push the TEMP SET and MODE buttons at the same
time and hold them for five seconds. "1", which means
diagnostic screen #1, will appear for two seconds. The
contents of diagnostic screen #1 will then appear until you
push the MODE button again.
Each time you push the MODE button, the next diagnostic
screen # appears for two seconds and then the contents of
the diagnostic screen appears. After screen # 9, the diagnos-
tic screens start again with screen #1.
Diagnostic Screen #1:
All display segments appear.
Diagnostic Screen #2:
No display segments appear.
Diagnostic Screen #3: Thermistor Temperature
The thermistor temperature appears in °F.
- The first digit of the temperature appears for one second
and the second digit of the temperature appears for one
second.
- Then no segments appear for a two second pause.
- This cycle repeats until you push the MODE button.
s e g m e n t 1
s e g m e n t 3
s e g m e n t 4
s e g m e n t 6
s e g m e n t 7 A rt01 075
Diagnostic Screen #4: Fault History
Individual segments appear for these recorded faults:
Segment 1 ............ Ignition fault.
Segment 2 ............ Door ajar.
Segment 3 ............ DC voltage low.
Segment 4 ............ DC voltage high.
Segment 5 ............ AC mode selected but not available.
Segment 6 ............ AC relay stuck closed.
Segment 7 ............ AC heater failed open.
Diagnostic Screen #5: Fault History - Continued
Individual segments appear for these recorded faults:
Segment 1 ............ Thermistor failure.
Segment 2 ............ Flame sense failure.
Diagnostic Screen #6: Erase Fault History
"E" appears for one second. Then "r" appears for one
second. After a two second pause, the cycle continues to
repeat as long as this display screen is active.
To erase the fault history:
- Push "TEMP SET" for five seconds.
- "C" appears for one second.
- Then "L" appears for one second.
- After a two second pause, the cycle continues to
repeat as long as this state is active.
- Push "TEMP SET" again for five seconds.
- "E" appears for one second.
- Then "r" appears for one second.
- After a two second pause, the cycle continues to
repeat as long as this display screen is active.
Diagnostic Screen #7: Inputs
Individual segments appear for these inputs to the refrigera-
tor controls:
Segment 1 ............ Door of the fresh food compartment is
closed and interior light is off.
Segment 2 ............ Burner flame is sensed.
Segment 3 ............ Thermistor is sensed.
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