Hoshizaki FS-1022MLH-C service manual Control Board Check

C. 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. Before proceeding, check for proper voltage per unit nameplate. Check that the 24VAC 1A fuse and the 115VAC 3A GM fuse are good. When checking for high‑voltage (115VAC), always choose a white (W) neutral wire to establish a good neutral connection. When checking for low-voltage (secondary) (24VAC), always choose a light blue (LBU) neutral wire to establish a good neutral connection. If the icemaker is in alarm, see "II.C.2. LED Lights and Audible Alarm Safeties."

Note: EH energizes when "GM" LED turns on. CB X1 Comp relay energizes PDS. Refrigeration circuit low-side pressure rises to 29 PSIG, closing the CLPS contacts. MC is energized when CLPS closes, energizing Comp and FMR.

1)Check the S1 dip switch settings to assure that they are in the factory default position.

For factory default settings, see "II.C.3.a) Default Dip Switch Settings." S1 dip switch

7 determines bin control application:

Bin Control Application:

Infrared Sensor Bin Control with Mechanical Backup Bin Control: S1 dip switch 7 in the "ON" position.

Mechanical Bin Control (Standard Ice Storage Bin): S1 dip switch 7 in the "OFF" position.

2)Startup – "POWER OK" LED on: Move the control switch to the "ICE" position, then move the power switch to the "ON" position. The "POWER OK" LED turns on. Diagnosis "POWER OK" LED: Check that the "POWER OK" LED is on. If not, check for proper supply voltage (115VAC) input to the CT (main breaker or fuse and power switch). Next, check for proper low-voltage (24VAC) output from CT and that the 1A fuse is good. Check for 24VAC from K8 connector pin #1 white/red (W/R) to

K8 connector pin #2 light blue (LBU). If 24VAC is present and the "POWER OK" LED is off, CB is bad and must be replaced.

3)IS Power Supply: CB supplies 20VDC to IS. Diagnosis: Check that IS green LED is on. If green LED is not on, check for 20VDC between CB connector K6 dark blue (DBU) and connector K6 brown (BR). See Fig. 1. If 20VDC is not present, CB is bad and must be replaced.

Infrared Sensor (20VDC)	Brown (BR)
Closed
20VDC DBU to BR
20VDC DBU to W
0VDC W to BR	White (W)

Infrared Sensor (20VDC)

Open (yellow LED flashing or steady)

20VDC DBU to BRDark Blue (DBU) 0VDC DBU to W

20VDC W to BR

Red Positive Test Lead

Black Negative

Test Lead

20VDC

Multimeter

Fig. 1	• K6 Connector
	Infrared Sensor

30