Service Diagnosis; Minute Diagnostic Procedure - Hoshizaki KM-40B Service Manual

IV. SERVICE DIAGNOSIS

1. 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 21°C or warmer air and 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. As you go through the
procedure, check to assure the components energize and de-energize correctly. If not,
those components and controls are suspect.
1) Turn power off and access the control box. Clear any ice from the bin control actuator
located in the bin.
2) Turn power on and place the control switch in the "ICE" position. A 5 second delay
occurs. The "POWER OK" LED on the control board comes on. If the "POWER
OK" LED is flashing (indicating a full bin), check the bin control. See "II. 5. [b] BIN
CONTROL CHECK PROCEDURE."
3) One Minute Fill Cycle – 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 water valve
does not open, check for no supply voltage at 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 board.
4) Initial Harvest Cycle – The inlet water valve remains energized, contactor coil
energizes to start the compressor (and fan motor on a remote condenser unit), and
the hot gas valve energizes. The evaporator warms and the thermistor senses 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 completes counting (1 to 3 minutes).
The unit then cycles to freeze. Diagnosis: Check if compressor is running, hot gas
valve is open, 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.
5) Freeze Cycle – The compressor remains energized, pump motor, (line valve if
applicable), and fan motor energize. The inlet water valve and hot gas valve de-
energize. The unit is held in freeze by a 5 minute short cycle protection timer which
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