Hoshizaki KM-420MWJ Service Manual page 39

4a) K Control Board (2A8242-02) - UBC control board green "LED 1" LED is on and CB
yellow "BC OPEN/CLOSED" LED is off.
a) Bin Empty Diagnosis: If fill cycle does not start, confirm UBC control board green
"LED 1" LED is on. If not, with UBC wire harness connected to CB K4 connector,
check for 5VDC at CB K4 pin #3 (W) to CB K4 pin #2 (BK). If 5VDC is not present,
replace CB. If 5VDC is present, check that the UBC wire harness is connected to the
UBC control board. If the UBC control board green "LED 1" LED is off, replace UBC
and UBC control board. If UBC control board green "LED 1" LED is on and icemaker
does not start, check for 1VDC at CB K4 pin #1 (R) to CB K4 pin #2 (BK). If 1VDC is
present, replace CB. If 4VDC is present, confirm no object is obstructing UBC lens. If
no obstruction, replace UBC and UBC control board.
Control Board K4 Bin Control Connector
Pin #
#1 to #2
#1 to #3
#2 to #3
b) As water begins to fill the water tank (1-min. fill), place an object 5" to 7" (127 to
178 mm) away from the UBC lens. See Fig. 7a.
UBC control board 5-sec. delay timer starts.
UBC control board 5-sec. delay timer terminates,
green "LED1" LED turns off and CB
"BC OPEN/CLOSED" LED turns on. CB 15-sec.
delay timer starts. CB 15-sec. delay timer terminates
and the icemaker shuts down. Remove the object
from the UBC lens. UCB control board 30-sec. delay
timer starts. UCB control board 30-sec. delay timer
terminates, CB "BC OPEN/CLOSED" LED turns off,
UBC control board green "LED 1" LED turns on, and the icemaker restarts.
Note: In some cases, removing the UBC sensor and rotating the UBC lens up and
down, provides better access when troubleshooting.
4b) K+ Control Board (2A9678-01) - CB yellow "BIN CLS" LED is off.
a) Bin Empty Diagnosis: As water begins to fill the water tank (1-min. fill), place an
object 5" to 7" (127 to 178 mm) away from the UBC lens. See Fig. 7b.
CB 5-sec. delay timer starts. "BIN CLS" LED turns
on. CB 5-sec. delay timer terminates, CB 15-sec.
delay timer starts. CB 15-sec. delay timer terminates
and the icemaker shuts down. Remove the object
from the UBC lens. CB 30-sec. delay timer starts.
CB 30-sec. delay timer terminates, CB "BIN CLS"
LED turns off, and the icemaker restarts. Note: In
some cases, removing the UBC sensor and rotating
the UBC lens up and down, provides better access
when troubleshooting.
ALARM RESET
Bin Empty (closed)
Wire Color
R to BK
R to W
BK to W
K2
1 2 3
39
OUTPUT TEST
VDC
1VDC
5VDC
UBC Wire Harness
5VDC
Connection
ON
1 2 3 4 5
CB
Fig. 7a
Bin Control Lens
Fig. 7b
Bin Control Lens