Hoshizaki Steelheart Series Service Manual page 18

2) Termination Diagnosis: There is a 5 min. minimum defrost time and a 1 hr.
maximum defrost time. Has 5-min. minimum defrost timer terminated? Confirm DTh
status. See "II.C. Thermistor Check."
(1) RCM, DTh, and DH Diagnosis: If 5-min. minimum defrost timer has terminated,
has DTh warmed to 41°F (5°C)? If not, check DST and DH continuity. Next,
check DH amp draw. If DTh is in proper range, DH de-energizes. If not, replace
RCM. If 41°F (5°C) is not achieved within 1 hr., RCM terminates defrost. Once
DH de-energizes or 1-hr. maximum defrost timer terminates, 3-min. drip off time
starts. (confirm)
(2) Comp/CondFM, EvapFM Diagnosis: 3-min. drip off time terminates. Comp,
ConFM energize. If DTh is 37°F (2.8°C) or higher when 3-min. drip off time
terminates, EvapFM(s) remains off until DTh is 36°F (2.2°C) or lower. If not,
confirm RTh is warm enough for Comp, ConFM, and EvapFM(s) operation.
Next, check for 115VAC at RCM 1(C) violet (V) wire to neutral white (W) wire.
If 115VAC is not present, check RTh status. "II.C. Thermistor Check." If RTh
ohm reading is in proper range and Comp and ConFM do not energize, replace
RCM. If 115VAC is present and Comp does not energize, check Comp external
overload. If open, let it cool and reset. If it does not reset, replace external
overload. If closed, check PTC relay, run capacitor, Comp windings for continuity,
or motor binding. If ConFM is not energized, check ConFM fan blades for binding
and winding continuity.
(3) EvapFM Diagnosis: 3-min. Comp/ConFM drip off time terminates. If DTh
is at 36°F (2.2°C) or lower, EvapFM energizes. If not, confirm that DTh is at
36°F (2.2°C) or lower. If not, confirm Comp is on and cooling. See "II.B.5)b)
Comp/ConFM Diagnosis" and "II.C. Thermistor Check." Once 36°F (2.2°C) or
lower is achieved, check for 115VAC at RCM 5(F) dark blue (DBU) wire to neutral
white (W) wire. If 115VAC is not present, replace RCM. If 115VAC is present,
and EvapFM(s) are not energized, check EvapFM(s) blades for binding and
EvapFM(s) windings continuity.
(4) CabFM Diagnosis: 3-min. drip off time terminates. If DTh is at 36°F (2.2°C) or
lower, CabFMR energizes. If not, check for 115VAC at CabFMR dark blue (DBU)
wire to neutral (W) wire. If 115VAC is not present and DTh is at 36°F (2.2°C)
or lower, replace RCM. If 115VAC is present and CabFM(s) are not energized,
check for 115VAC at CabFMR yellow (Y) wire to neutral white (W) wire. If 115VAC
is not present, check temperature at CTh. CabFM(s) de-energize when CTh is
below CCM setpoint. Once CTh temperature reaches 1.8°F (1°C) above setpoint,
check for 115VAC at CCM 3(F) yellow (Y) wire to neutral white (W) wire. If
115V is not present, replace CCM. If 115VAC is present and CabFM(s) are not
energized, check CabFM(s) blades for binding and CabFM(s) winding continuity.
If there is no continuity, replace CabFM(s).
Legend: CabFM–cabinet fan motor; CabFMR–cabinet fan motor relay; CCM–cabinet
control module; Comp–compressor; ConFM–condenser fan motor; CTh–cabinet
thermistor; DH–defrost heater; DST–defrost safety thermostat; DTh–defrost
thermistor; EvapFM–evaporator fan motors; RCD-rail control dial; RCM–rail control
module; RLSen-rail light sensor; RTh–rail thermistor
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