Hoshizaki HR24A service manual B. Control Board Check, Startup and Cool Down, 10Defrost

B. Control Board Check

Before replacing a CB 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. Always choose a neutral (W wire) to establish a good neutral connection when checking AC voltage (115VAC).

Startup and Cool Down:

1)Press the power button for 2 sec. to turn off the appliance.

2)Unplug the appliance from the electrical outlet.

3)Remove the top panel. Check all wiring connections. Confirm that the power cord, EvapFM, Comp, DS, and CTh are all properly connected to CB and ground connection (GND) is properly connected to the frame.

4)Secure the top panel to prevent it from falling over when checking voltages and

CB items.

5)Secure (tape) DS in the door closed position.

6)Plug the appliance back in. °F LED turns on. Diagnosis: Confirm that °F LED is on. If not, check CB POWER connector for 115VAC. If 115VAC is not present, check power supply and power cord connection. If 115VAC is present and °F LED is not on, replace CB.

7)Press the power button for 2 sec. to turn on the appliance.

8)Check that CT LEDs and EvapFM icon turn on. If not, check for 115VAC at the POWER connector on CB. If 115VAC is not present, check power cord and power supply.

If 115VAC is present, and DM is not on (°F and CT LEDs and EvapFM icon), replace CB.

9)If °F and CT LEDs are on but EvapFM icon is not, confirm DS is engaged (pushed in, contacts open). Check across DS for 5VDC. If 5VDC is not present, check DS activation lever and DS continuity. Note: DS contacts are open when DS is engaged (door closed). If 5VDC is present, check CB EvapFM connector for 12VDC. If 12VDC is not present, replace CB. If 12VDC is present, check EvapFM wiring connector for loose connection, EvapFM continuity, and fan blade for binding.

10)Defrost:

This appliance defrosts every 6 hrs. for 30 min. Defrost is an off-cycle defrost.

a)Manual Defrost Initiation: To initiate a manual defrost, press and hold the "+" button until the defrost icon turns on. 30‑min. DT starts. EvapFM continues. If Comp run time < 3 min., Comp icon and Comp continue until 3-min. Comp run timer terminates. Once 3-min. Comp run timer terminates, Comp icon turns off, Comp de‑energizes, and 30-min. DT starts. Diagnosis: If defrost icon is on, confirm that Comp de‑energizes. If not, confirm Comp run time > 3 min. If Comp continues after 3-min. Comp run timer terminates, replace CB.

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