Hoshizaki MRH KM-901MAH, MWH KM-515MAH, MRH/3, MWH(-M), MRH KM-600MAH KM-650MAH G Control Board

2. "G" Control Board

At startup, a 5-second delay occurs while the control board conducts an internal timer check. A beep occurs when the control switch is moved to the "ICE" position. The red "POWER OK" LED indicates proper control voltage and remains on unless a control voltage problem occurs. The green LEDs 1 through 4 energize and sequence from initial startup as listed in the table below. Note that the order of the LEDs from the outer edge of the control board is 1, 4, 3, 2.

Sequence Step		LED		Energized			Time LEDs are On
				Components	Min.		Max.	Avg.
1-Minute Fill Cycle	4			WV				1 minute
Harvest Cycle		1, 4, 2		Comp, FMR, HGV, WV	2 minutes		20 minutes	3 to 5 minutes
Harvest Pump Timer	1, 3, 2			Comp, FMR, HGV, PM	0 seconds		50 seconds	harvest pump timer
								setting
Freeze Cycle	1			Comp, FM/FMR, PM,	5 minutes		freeze timer	30 to 35 minutes
				LLV			setting
Pump-Out Cycle		1, 4*, 3, 2	Comp, FMR, HGV, PM,		10 seconds	20 seconds		*pump‑out timer
				WV*				setting

The built-in safeties shut down the icemaker and have alarms as listed below.

No. of Beeps	Type of Alarm	Notes
(every 3 sec.)
1	High Evaporator Temp.	Check for harvest problem (stuck HGV or relay), hot
	(temperature > 127°F) (53°C)	water entering icemaker, or shorted thermistor.
2	Harvest Backup Timer	Check for open thermistor, HGV not opening, TXV or
	(harvest > 20 min. for two	LLV leaking by, low charge, or inefficient Comp, or WRV
	cycles in a row)	leaking by.
3	Freeze Timer	Check for FS stuck closed (up), WV leaking by, HGV
	(freeze > freeze timer setting	leaking by, PM not pumping, TXV not feeding properly,
	for two cycles in a row)	LLV not opening, low charge, HM not bypassing, or
		inefficient Comp.
To reset the above safeties, press the "ALARM RESET" button with the power supply on.
6	Low Voltage	Red LED turns off if voltage protection operates.
	(92Vac±5% or less)	The control voltage safeties automatically reset when
7	High Voltage	voltage is corrected.
	(147Vac±5% or more)

Legend: Comp–compressor; FM–fan motor; FMR–fan motor remote; FS–float switch; HGV–hot gas valve; HM–headmaster (C.P.R.); LLV–liquid line valve; PM–pump motor; TXV–thermostatic expansion valve; WRV–water regulating valve; WV–inlet water valve

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