Control Board Check - Hoshizaki KM-901MAH Service Manual

7) Normal Harvest Cycle – same as the initial harvest cycle – See "IV.A.4) Initial Harvest
Cycle."
8) Shutdown
a) Thermostatic Bin Control: Auxiliary Code T-0, U-0
When the unit is running hold ice in contact with the thermostatic bulb, TBC
switch opens within 10 seconds, shutting down the unit. TBC is factory set, and
generally no adjustment is required. However, adjustment may be needed in
some conditions, particularly at higher altitude locations. CAUTION! Do not
adjust S4 dip switch 7 out of the factory default position on this model.
This dip switch must be left in the factory default position or this unit
will not operate correctly. Diagnosis: See "IV.C.1. Thermostatic Bin Control
Check."
b) Mechanical Bin Control: Auxiliary Code U-1 and Later
See "IV.C.2.a) Mechanical Bin Control Check."
Legend: CB–control board; Comp–compressor; FM–fan motor; FMR–fan motor-remote;
F/S–float switch; HGV–hot gas valve; HM–headmaster (C.P.R.); LLV–liquid line
valve; MBC–mechanical bin control; PM–pump motor; TBC–thermostatic bin
control; TXV–thermostatic expansion valve; WV–inlet water valve
B. Control Board Check
Before replacing a control board that does not show a visible defect and that you
suspect is bad, always conduct the following check procedure. This procedure will help
you verify your diagnosis.
Alarm Reset: If the control board is in alarm (beeping), press the "ALARM RESET"
button on the control board with power on. Once reset, the unit starts at
the 1-minute fill cycle. For audible alarm information, see "II.C.2.f) LED
Lights and Audible Alarm Safeties."
1) Check the dip switch settings to assure that S4 dip switch 3, 4, 7, 8, 9, & 10 and
S5 dip switch 1 through 5 ("G" control board) are in the factory default position. S4 dip
switch 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."
2) Move the control switch to the "ICE" position. If the red "POWER OK" LED is on, the
control voltage is good. If the "POWER OK" LED is off, check the control transformer
secondary circuit. The control transformer secondary circuit includes the cleaning valve
interlock switch. Make sure the interlock switch is closed; otherwise, no control voltage
is supplied to the K2 connector. Transformer output is 10.5V at 115V primary input. If
the secondary circuit has proper voltage and the red LED is off, the control board is
bad and should be replaced. See "V.P. Removal and Replacement of Control Board."
If the secondary circuit does not have proper voltage, check the control transformer
primary circuit. Check for 115V at the control board K1 ten-pin connector. Check the
#10 pin (BR wire) to a white neutral wire for 115V. Always choose a white neutral wire
to establish a good neutral connection when checking voltages. For additional checks,
see "IV.F.1.[1] The icemaker will not start."
53