Service Diagnosis; 10-Minute Diagnostic Procedure - Hoshizaki KML-351MAH Service Manual

IV. Service Diagnosis
A. 10-Minute 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 (21°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
dip switch settings to assure that #3, 4, 7, 8, 9, & 10 are in the factory default position.
Switches 1, 2, 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 K1 connector.
1) Turn off the power supply and access the control box.
2) Turn on the power supply and move the control switch to the "ICE" position. A 5 second
delay occurs. The red "POWER OK" LED on the control board 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 or bad 1 minute timer in the 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 fan motor on
a remote air-cooled unit), and the hot gas valve energizes. The inlet water valve is
open during harvest for a maximum of six minutes or the length of harvest which ever
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. The timer has settings of 60, 90, 120, and 180 seconds
(dip switch 1 & 2). When the harvest timer countdown is complete, 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 2 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, the
discharge line temperature, compressor efficiency, and if the hot gas valve is fully open.
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