Service Diagnosis; Diagnostic Procedure - Hoshizaki DCM-500BAH Service Manual

IV. Service Diagnosis
A. Diagnostic Procedure
This diagnostic procedure is a sequence check that allows you to diagnose the electrical
system and components. Before proceeding, check for correct installation, adequate
water supply (minimum of 10 PSIG, maximum of 113 PSIG) and proper voltage per unit
nameplate. Always choose a white neutral wire to establish a good neutral connection
when checking voltages. LEDs on the control board correspond to the components as
they energize.
1) Move the control switch to the "OFF" position, then turn off the power supply. Remove
the upper and lower front panels. Confirm the power switch is in the "ON" position and
the door switch is engaged.
) Turn on the power supply, then move the control switch to the "ICE" position. The
"POWER" LED is on. The "POWER" LED will not come on if the door switch is not
engaged.
3) Fill Cycle – The inlet water valve energizes. The reservoir fills. The lower float switch
closes. Nothing occurs at this time. The reservoir continues to fill until the upper float
switch closes, energizing the water control relay, which closes the low water safety
circuit and de-energizes the inlet water valve. Diagnosis: Check that the inlet water
valve fills the reservoir. If not, check for water supply line shut-off valve closed, clogged
water filters, clogged inlet water valve screen, power circuit to the inlet water valve
(power switch, door switch, power protect relay contacts, transformer, fuses, high
pressure switch, bin control, control switch, float switch, water control relay contacts),
and the coil on the inlet water valve. Check that the inlet water valve shuts off when
the upper float switch closes. If not, check the float switch, water control relay, and inlet
water valve.
4) Ice Purge Cycle – "GM" LED is on (60 second short cycle protection). The 60 second
timer starts, the gear motor protect relay and gear motor energize. Diagnosis: Check
that the gear motor starts. If not, check that the water control relay is energized (inlet
water valve should be closed). Check the low water safety circuit on the water control
relay (terminals 4 and 6), check for 115/10V at the K1 connector "COM" terminal to
neutral and "NO" terminal to neutral on the control board (see wiring diagram), check
the gear motor fuse (overload protector), thermal protector, gear motor capacitor, and
motor windings. If the gear motor starts, but the auger does not turn, check the gear
motor coupling between the auger and the gear motor. If the compressor starts at the
same time the gear motor starts, check the X compressor relay on the control board.
5) Freeze Cycle – "GM", "COMP" LED are on. The compressor and fan motor energize,
the gear motor protect relay, gear motor, and water control relay remain energized. Ice
production begins 4 to 6 minutes after the compressor and fan motor start depending
on ambient and water temperature conditions. Diagnosis: Check that the compressor
and fan motor are running. If not, check for voltage on and to the compressor (X relay
on the control board). Check that the gear motor protect relay circuit terminals 3 and 5
are closed, check the compressor internal overload (thermal protector), the compressor
capacitors, fan capacitor, and voltage to the fan motor.
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