Service Diagnosis; 10-Minute Km Diagnostic Procedure - Hoshizaki KM1601SRH350 Service Manual

III. Service Diagnosis
A. 10-Minute KM Diagnostic Procedure
The 10 minute check out procedure is basically a sequence check which can be used
at unit start-up or for system diagnosis. Using this check out procedure will allow you
to diagnose electrical system and component failures in approximately 10 minutes
under normal operating conditions of 70°F (1°C) or warmer air and 50°F (10°C) or
warmer water temperatures. Before conducting a 10 minute checkout, check for correct
installation, proper voltage per unit nameplate, and adequate water supply. Check the
S4 dip switch settings to assure that they are in the factory default position. Switches
1, , 5, & 6 are cleaning adjustments and the settings are flexible. For factory default
settings, see "II.C.3.a) Default Dip Switch Settings." As you go through the procedure,
check to assure the components energize and de-energize correctly. If not, those
components and controls are suspect. Check for voltage at the control board K1 10-pin
connector.
1) Turn off the power supply and access the control box.
) Turn on the power supply and move the control switch to the "ICE" position. A 5-second
delay occurs. The red "POWER OK" LED comes on.
3) One Minute Fill Cycle – LED 4 is on. The inlet water valve is energized. After
1 minute, the control board checks the float switch. If the float switch is closed, the
unit cycles to harvest. If closed, continue to step 4. If the float switch is open, the unit
repeats the 1 minute fill cycle until water enters and the float switch closes (low water
safety protection during initial start up and at the end of each harvest). Diagnosis: If
the inlet water valve does not open, check for no supply voltage at the inlet water valve
terminals, bad coil, or plugged screen or external filter (no water flow). If unit fails to
start harvest, check for open float switch (see "II.E. Float Switch") or bad 1 minute timer
in control board.
4) Initial Harvest Cycle – LEDs 1, 4, and 2 are on. The inlet water valve remains
energized, the contactor coil energizes to start the compressor (and the fan motors on
remote air-cooled models), and the hot gas valve energizes. The inlet water valve is
open during harvest for a maximum of 6 minutes or the length of harvest, whichever
is shorter. The evaporator warms and the thermistor senses 48°F (9°C). The control
board then receives the thermistor's 3.9 kΩ signal and turns operation of harvest over
to the harvest timer (S4 dip switch 1 & ). The timer has settings of 60, 90, 10, and
180 seconds (S4 dip switch 1 & ). When the harvest timer countdown is complete
(1 to 3 minutes), the freeze cycle starts. Diagnosis: Check if compressor is running,
hot gas valve is open, inlet water valve still open. Average harvest cycle at factory
setting is  to 3 minutes. How long does initial harvest last? 1.5 minutes after initial
harvest begins, touch the compressor discharge line. Is it hot? If not, check refrigerant
pressures and compressor operation. If it is hot, touch the inlet line to the evaporator.
Is it hot? If it is hot and the freeze cycle is not starting, check the harvest timer
adjustment, the thermistor for open circuit (see "II.D.1. Thermistor Check Procedure"),
the discharge line temperature, compressor efficiency, and if the hot gas valve is fully
open.
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