Hoshizaki KM-1340MAH, Service Manual

13

B. Sequence of Operation

The steps in the sequence are as outlined below. When power is supplied, a 5 second 
delay occurs at startup. Note that the order of the LEDs from the outer edge of the board is 
1, 4, 3, 2.

1. One Minute Fill Cycle

LED 4 is on. WV opens and the fill period begins. After 1 minute, the board checks for 
a closed F/S. If F/S is closed, the harvest cycle begins. If not, WV will remain energized 
through additional 1 minute cycles until water enters the sump and F/S closes. This serves 
as a low water safety to protect the water pump.

2. Initial Harvest Cycle 

LEDs 1, 4, and 2 are on. WV remains open, Comp and FMR energize, HGV opens, 
and harvest begins. As the evaporator warms, the thermistor located on the suction line 
checks for a 48°F (9°C) temperature. When 48°F (9°C) is reached, a 3.9 k

Ω

 signal turns 

the harvest over to the adjustable harvest timer which is factory set for normal conditions. 
The timer has settings of 60, 90, 120, and 180 seconds (dip switch 1 & 2). The water valve 
is open during harvest for a maximum of 6 minutes or the length of harvest, whichever is 
shorter. When the harvest timer completes its count down, the harvest cycle is complete 
and the freeze cycle starts. The minimum total time allowed by the board for a complete 
harvest cycle is 2 minutes.

3. Freeze Cycle 

LED 1 is on. Comp and FMR continue to run, PM and FMS energize, LLV opens, HGV 
and WV close and the freeze cycle starts. For the first 5 minutes the control board will not 
accept a signal from F/S. This 5 minute minimum freeze acts as a short cycle protection. At 
the end of 5 minutes, F/S assumes control. As ice builds on the evaporator the water level 
in the sump lowers. The freeze continues until F/S opens and terminates ice production.

4. Pump-Out Cycle 

LEDs 1, 3, and 2 are on. Comp and FMR continue to run, HGV opens, LLV closes, and 
FMS deenergizes. PM stops for 2 seconds and reverses, taking water from the bottom of 
the sump and forcing pressure against the check valve seat allowing water to go through 
the check valve and down the drain. At the same time water flows through the small tube 
to power flush the F/S. When the pump-out timer stops counting, the pump out is complete. 
Pump out always occurs on the 2nd harvest after startup. Then, depending on the control 
board setting, pump out occurs every cycle, or every 2nd, 5th or 10th cycle (dip switch 5 & 
6).

5. Normal Harvest Cycle 

LEDs 1, 4, and 2 are on. Comp and FMR continue to run, HGV remains open and WV 
opens. As the evaporator warms, the thermistor reaches 48°F (9°C). The control board 
then receives the thermistor's 3.9 k

Ω

 signal and starts the harvest timer. The water valve 

is open during harvest for a maximum of 6 minutes or the length of harvest, whichever is 
shorter. When the harvest timer completes its count down, the harvest cycle is complete 
and the next freeze cycle starts. The unit continues to cycle through 3, 4 and 5 sequence 
until the bin control senses ice and shuts the unit down.

Legend: 

Comp–compressor; FMR–remote fan motor; FMS–self-contained fan motor; 

F/S–float switch; HGV–hot gas valve; LLV–Liquid Line Valve; PM–pump motor;    

WV–inlet water valve