This video will demonstrate the proper way to perform the ten-minute checkout procedure for
a system diagnosis of the KM Cuber. Before we see how to diagnose electrical and component failures,
let's review the KM Cuber's sequence of operation. First, the unit always starts in
the one-minute fill cycle. 60 seconds later the initial harvest begins. Three to four minutes
later the freeze cycle begins. Longer harvest may occur in colder climates. After an average freeze
time of approximately 30 minutes, the pump out cycle occurs. 10 to 20 seconds later the normal
harvest begins. The KM Cuber will continue to cycle until the bin control opens to stop the
ice production. The first step in the ten-minute checkout procedure is to make sure there is
adequate water and power supply to the unit. When troubleshooting for system failures, remove the
front panel, turn the ice maker off, and remove the control box cover. Now turn the unit back on,
remove the evaporator cover, and make sure water is entering the reservoir. If there is no water
coming in, check the bin control. The bin control contacts supply power to all the other controls in
the unit. To check the bin control, flip the unit switch to the wash position. If the pump starts it
indicates that the bin control is closed. Next, check the cleaning valve micro switch. Flip the
unit switch back to the ice making position. If there is still no water entering the evaporator,
check the position of the cleaning valve handle. This handle must be in the horizontal position in
order for the micro switch located behind the handle to close. This micro switch supplies
control voltage to the control board. The cycle will not start without control voltage. A quick
check of the control transformer secondary will verify that control voltage is present. If the
one-minute fill does not begin after you have checked the bin control and cleaning valve,
check for 115 volts to the water valve. Check the terminals of the inlet water valve,
if you have voltage you can assume there is a problem with the water valve. Before
replacing the water valve, check the inlet screen for debris. To do this,
shut off the water and unscrew the thumb nut behind the water valve. Push the waterline
aside and inspect the screen. Clean or replace the screen as necessary. Check the water valve
coil and diaphragm for problems and replace the valve if necessary. After correcting the
water valve problem, turn the machine on. The ice maker should cycle through the one-minute fill and
start the initial harvest cycle. If the initial harvest cycle does not start after one minute,
check the float switch. Unplug the float switch and check for continuity with your
own meter. If it is not closed and water is in the reservoir, the float switch is either dirty
or defective. Clean it and check it to assure proper operation. If the float switch is good,
the control board timer is defective and the board should be replaced. If the ice maker cycles into
the initial harvest, the float switch is closed and the one-minute timer works. A minute or so into the
harvest cycle the inlet to the evaporator should feel warm to the touch. As the hot gas circulates,
the thermistor at the evaporator outlet reaches 48 degrees. The length of time it takes to reach
48 degrees depends on the ambient conditions and the water temperature. The length of harvest will
automatically adjust to be longer in the winter and shorter in the summer. If the evaporator is
not warming up, the first place to check is the hot gas valve. Lightly touch the discharge line
to see if it is hot. If the discharge is not hot, then there is an obvious refrigeration problem
and you'll have to troubleshoot the system using basic refrigeration practices. If the discharge
line is hot, but there is no heat coming from the outlet of the hot gas valve to the evaporator, you
should check for coil voltage. To check for voltage, pull the tin pin connector out about 3/8 of an inch
and check from the pen on the pink wire, which is the hot gas valve to a neutral white wire. If you
get proper voltage, the control board is working. If not, the problem is the control board. If you
do get voltage, check the coil to be sure it's energized. To do this, lay a metal paperclip on
the coil. If you can feel a magnetic pull, the coil is energized. If the coil is in fact energized, it
is possible that the hot gas valve is stuck. A stuck valve should be replaced using proper
refrigeration practices. With normal operation of the hot gas valve the evaporator will warm. At 48
degrees the thermistor will start the defrost completion timer. The average harvest cycle and
average ambient temperatures will range from two to four minutes. Longer harvest will occur with colder
supply water or if the defrost completion timer is adjusted longer. If the harvest cycle does not
end within ten minutes, leave the machine running and unplug the thermistor. Check the resistance
with your own meter and compare it against the temperature resistance chart in your tech specs
book. For example, if your meter reads 6K ohms of resistance, the sensor temperature is 32 degrees.
However, after ten minutes in the harvest cycle the temperature should be much warmer. This would tell
you that there is a refrigeration problem. In another example, if your meter reads 2.5K ohms
then the suction line temperature is 70 degrees. Since that temperature is well above the normal
48 degrees needed to start the defrost completion timer, the control board is not responding and
there is a problem with the board. Once the harvest cycle ends, the freeze cycle begins.
The hot gas valve and water valve de-energize and the pump motor and self-contained fans start.
After the ice maker is in the freeze cycle, the evaporator inlet should feel cold within about
three minutes. If it does, you have basic refrigeration occurring. If the evaporator is still warm after three
minutes, there is a possible refrigeration problem. This problem might be caused by, one: hot gas valve
not closing, two: coils still energized because of a control board problem, three: thermostatic expansion
valve not opened properly, or four: insufficient refrigerant. These items should be checked using
normal refrigeration diagnostic practices. Next, let's make sure the icemaker is purging properly
by checking the pump out system. After five minutes in the freeze cycle, unplug the float switch to
initiate harvest. This will cause the unit to go into a ten-second pump out that will flush the
dirty water and sediment through the check valve and down the drain. You could also squeeze the pump
supply hose tight enough to force the water down the drain. This would empty out the reservoir and
allow the float switch to open by itself. It is important to understand the control components
of the KM Cuber. These components include the control board, the float switch, the thermistor, and
bin control. First, let's look at the bin control for any suspected problems or adjustments. A quick
check of the bin control can be accomplished by switching the pump to the wash position. The unit
will not start if the bin control is stuck open. When the bin control is stuck closed, the machine
will not automatically shut off. If the bin control is not adjusted properly, it could cause the unit
to shut down prematurely or allow ice to back up into the evaporator, causing a freeze up condition.
To check the adjustment of the bin control, access the thermostatic bulb. Turn the switch to the wash
position. Next, place a small amount of ice on the thermostatic bulb. Count the seconds and listen
for the pump to shut off. If the pump shuts down within six to ten seconds, the bin control
is adjusted properly. Adjustment can be made with a screw driver in the bin control slot. The float
switch has two primary functions; it provides low water safety protection and initiates harvest. If
the float sticks in the down position, which is open, the unit will switch to the one-minute fill
cycle and run water continuously. If the float sticks in the up position, which is closed, the
unit will remain in freeze for 60 minutes. The cubes will be larger than normal and the pump
will cavitate before harvest begins. If either of these symptoms exist, the float switch needs to be
cleaned and checked. First, take the float switch apart and clean it with ice machine cleaner. Once
you've cleaned the float switch, check it with an ohm meter to be sure it operates properly.
The thermistor monitors the outlet temperature of the evaporator. At 48 degrees it starts the defrost
completion timer. At 127 degrees it automatically shuts down the machine on the manual reset high
temperature safety. There are only two ways a thermistor can fail; open or shorted. An open
thermistor will cause a consistent 20 minute harvest cycle. A shorted thermistor will shut
the unit down on the high temperature safety. When you switch the power off and back on the
safety will not reset. The thermistor should be checked using an ohm meter as previously
discussed. Now, the control board. The control board processes information to supply the voltage that
allows the components of the ice maker to cycle properly. Many things can affect the control
board, but if you have proper supply voltage, proper control voltage, a good float switch, a
good thermistor, and good pin connections, and the machine is not cycling properly, you can assume
that you may have to replace the control board. Remember, when servicing any Hoshizaki ice maker,
always refer to your tech specs guide for detailed information or call the Hoshizaki service hotline
on your screen. Understanding these symptoms and the operation of these simple controls
will help you diagnose sequence problems on a KM unit using the ten-minute checkout procedure.
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