Not Heating; Over Temperature; Not Filling; Not Draining - GE Monogram ZBD6400 Series Technical Service Manual

6000 & 7000 Series DISHWASHERS
4.3

NOT HEATING

During a heating cycle, if the water temperature sensed has
not been rising by greater than 9 deg F in 15 minutes, the
heating element relay is to be de-energized and wash
program operation is to continue until the maximum time in
that heating step has been reached, the program is then to
proceed to the next step. A not heating fault code is to be
saved in memory for fault diagnosis during service.
4.4

OVER TEMPERATURE

If at any time water temperature sensed exceeds 180º F,
program operation is to continue as normal, (without affecting
the wash program execution in any way), and an over-
temperature fault code is to be saved in non volatile memory
for fault diagnosis during service.
4.5

NOT FILLING

If the controller has not sensed that the pressure switch has
opened (water present) after the selected fill time, (refer
section 4.10.8 FILL LEVEL), (this is a prerequisite for pump
operation), the fill mode shall continue for a further 15
seconds or until the pressure switch opens, whichever occurs
first. If the pressure switch opens during the 15-second
period, the cycle shall continue, with total fill time remaining
as specified in the wash program. If the pressure switch does
not open after the additional 15 seconds, the control is to turn
off all outputs, indicate a not filling fault code to the user,
(refer section 4.1.3 IDENTIFYING FAULTS), and then save
the not filling fault code in non volatile memory.

4.6 NOT DRAINING

If the controller has not sensed that the machine is empty
after 5 minutes of draining, then the control is to turn off all
outputs, indicate a not draining fault code to the user, (refer
section 4.1.3 IDENTIFYING FAULTS), and then save the not
draining fault code in non volatile memory.
4.7

OVERFILL

Overfill detection is to have a 1-second steady state signal
before implementing.
The drain output is to be continuously monitored by the
control system. Whenever the drain output goes to active
potential other than in a normal drain cycle (i.e.. Leak Detec-
tion Switch or 2 nd level pressure switch closed) the control is
to save in nonvolatile memory the overflow fault code and
continue the wash program.
4.8

TURBIDITY SENSOR FAILURE

A two-stage scheme is used for fault detection:
First stage – "fault suspected": when a fault is first sensed, a
fault suspected flag is set
Second stage – "fault found": if the fault is sensed again the
fault found flag is set
The second stage decides that the dishwasher system must
run the default wash cycle, but if the fault was not sensed for
a second time then the fault suspected flag is reset and the
fault has been corrected.
To increase the signal to noise ratio of the turbidity measure-
ment each turbidity value is an average of the current value
with the previous values and this represents one period of
measurement.
There are 4 failure modes:
a. Low signal failure mode- the calibration routine ceases
and the dishwasher system invokes the default wash cycle.
This fault is non-correctable, does not have a fault suspected
mode and the Low signal fault flag is set
b. High signal failure mode - the same like above but the
High signal fault flag is set
Observation: a. & b. occurs when the calibration routine sets.
c. No signal failure mode - occurs when the turbidity sen-
sor outputs no pulses (if the receiver failed or a dishwasher
anomaly disrupts the signal from the receiver; if the LED
failed the receiver could continue to send pulses, less than
200 in the measurement interval)
During the calibration phase if the sensor output is less than
200 pulses in the maximum interval of 3 seconds, then the
Low signal fault is set. This condition is tested for each
turbidity measurement. If fault is suspected, then the routine
starts a counter, which will notify the fault detector when to
check the average count value again. The next check will be
after 4 samples of turbidity causing the detection period to
occur over 8 samples of turbidity. If the new average value is
again below the lower limit then the fault found flag is set and
the system notifies a No signal fault.
d. Turbidity temperature sensor failure mode – when the
control senses constant, abnormal voltages from turbidity
temperature sensor. This condition for sensor fault is checked
during each turbidity measurement.
This is a nonrecoverable fault the system invokes the default
wash cycle.
The following LEDs are used to indicate the faults:
Low signal failure mode
High signal failure mode
No signal failure mode
Turbidity temperature sensor failure mode - LED 4hr.
4.9

DOOR THERMISTOR FAILURE

During the wash cycle when door temperature is monitored,
temperature sampling result is to be checked, in order to
identify if the door thermistor is faulty.
If the Temperature sensed is below 32°F, then an Open
Circuit Door Thermistor fault code is to be saved in memory
for fault diagnosis during service.
If the Temperature sensed is above 210°F, then an Short
Circuit Door Thermistor fault code is to be saved in memory
for fault diagnosis during service.
If a door thermistor fault is detected during a wash and heat
step of a cycle, then the heating element relay is to be de-
energized, and wash program operation is to continue until
the maximum time in that heating step has been reached, the
program is then to proceed to the next step.
- LED 2hr
- LED High Temp.
- LED 2hr.
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