Hoshizaki Steelheart UR/WR27B Series User manual

Models
Undercounter
Worktop
Prep Table
Refrigerated Kitchen Equipment
Steelheart B Series
Service Manual
Number: 73247
Issued: 3-22-2021
Revision: 7-6-2022
hoshizakiamerica.com

2
WARNING
Only qualied service technicians should install and service the appliance. To
obtain the name and phone number of your local Hoshizaki Certied Service
Representative, visit www.hoshizaki.com. No service should be undertaken until
the technician has thoroughly read this Service Manual. Failure to service and
maintain the appliance in accordance with this manual will adversely affect safety,
performance, component life, and warranty coverage. Proper installation is the
responsibility of the installer. Product failure or property damage due to improper
installation is not covered under warranty.
Hoshizaki provides this manual primarily to assist qualied service technicians in the
service of the appliance.
Should the reader have any questions or concerns which have not been satisfactorily
addressed, please call, send an e-mail message, or write to the Hoshizaki Technical
Support Department for assistance.
Phone: [phone]
Fax: [phone]
E-mail: [email protected]
618 Highway 74 South
Peachtree City, GA 30269
Attn: Hoshizaki Technical Support Department
Web Site: www.hoshizaki.com
NOTE: To expedite assistance, all correspondence/communication MUST include the
following information:
• Model Number
• Serial Number
• Complete and detailed explanation of the problem.

3
IMPORTANT
This manual should be read carefully before the appliance is serviced. Read
the warnings and guidelines contained in this booklet carefully as they provide
essential information for the continued safe use, service, and maintenance of the
appliance. Retain this booklet for any further reference that may be necessary.
CONTENTS
Important Safety Information ................................................................................................. 4
I. Construction and Refrigeration Circuit Diagram ................................................................. 8
A. Construction.................................................................................................................. 8
B. Refrigeration Circuit Diagram...................................................................................... 10
II. Sequence of Operation and Service Diagnosis................................................................11
A. Sequence of Operation Flow Chart..............................................................................11
1. UR/WR: Refrigerator ...............................................................................................11
2. SR: Refrigerator..................................................................................................... 12
3. UF/WF: Freezer ..................................................................................................... 13
B. Service Diagnosis ....................................................................................................... 14
1. Diagnostic Procedures ........................................................................................... 15
C. Control Module Check................................................................................................. 20
D. Thermistor Check........................................................................................................ 23
E. Diagnostic Table.......................................................................................................... 24
III. Controls and Adjustments............................................................................................... 27
A. Temperature Settings .................................................................................................. 27
B. Defrost......................................................................................................................... 28
C. Safety Devices ............................................................................................................ 29
D. Perimeter and Mullion Heaters (UF/WF only).............................................................. 29
IV. Refrigeration Circuit and Component Service Information.............................................. 30
A. Refrigeration Circuit Service Information .................................................................... 32
B. Component Service Information.................................................................................. 35
V. Preparing the Appliance for Periods of Non-Use ............................................................. 36
VI. Disposal.......................................................................................................................... 37
VII. Technical Information..................................................................................................... 38
A. Electrical and Refrigerant Data ................................................................................... 38
B. Wiring Diagrams.......................................................................................................... 39
1. UR/WR27, UR/WR36, UR/WR48 (except glass door), and SR36.......................... 39
2. UF/WF27, SR27, and SR48.................................................................................... 40
3. UR/WR48 (glass door), UR/WR60, and UR/WR72............................................... 41
4. UF/WF48, UF/WF60, SR60, and SR72................................................................. 42

4
DANGER
Risk of Fire or Explosion
Flammable Refrigerant Used
• Follow handling instructions carefully
in compliance with U.S. government
regulations.
• Do not use mechanical devices to defrost.
• Do not puncture refrigerant tubing. Risk
of re or explosion due to puncture
of refrigerant tubing; follow handling
instructions carefully.
• Component parts shall be replaced with
like components.
• Servicing shall be done by factory
authorized service personnel to minimize
the risk of possible ignition due to incorrect
parts or improper service.
• Consult instruction manual/service manual
before attempting to install or service this
product. All safety precautions must be
followed.
• Dispose of properly in accordance with
federal or local regulations.
• Do not place any potential ignition sources
in or near the appliance.
Important Safety Information
Throughout this manual, notices appear to bring your attention to situations which could
result in death, serious injury, damage to the appliance, or damage to property.
DANGER Indicates a hazardous situation that, if not avoided, will result in
death or serious injury.
WARNING Indicates a hazardous situation that, if not avoided, could result
in death or serious injury.
NOTICE Indicates a situation that, if not avoided, could result in damage
to the appliance or property.
IMPORTANT Indicates important information about the use and care of the
appliance.
Risque De Feu Ou D'Explosion
Le Frigorigène Est Inammable
• Suivre attentivement les instructions
de manipulation conformément à la
réglementation gouvernementale.
• Ne pas utiliser d'appareils mécaniques
pour dégivrer le réfrigérateur.
• Ne pas perforer la tubulure contenant le
frigorigène. Risque de feu ou d'explosion
si la tubulure contenant le frigorigène
est perforée; suivre les instructions de
manutention avec soin.
• Les pièces des composants doivent être
remplacées par des pièces et accessoires
équivalents.
• L’entretien doit être effectué par le
personnel de service autorisé par le
fabricant an de minimiser les risques
d’inammation attribuables à l’installation
d’une pièce inadéquate ou à la mauvaise
exécution du service.
• Consulter le manuel du propriétaire/
guide de réparation avant de tenter une
réparation. Toutes les mesures de sécurité
doivent être respectées.
• Éliminer conformément aux règlements
fédéraux ou locaux.
• Ne placez aucune source d’inammation
potentielle dans ou près de l’appareil.

5
WARNING
The appliance should be destined only to
the use for which it has been expressly
conceived. Any other use should be
considered improper and therefore
dangerous. The manufacturer cannot be
held responsible for injury or damage
resulting from improper, incorrect, and
unreasonable use. Failure to install,
operate, and maintain the appliance
in accordance with this manual will
adversely affect safety, performance,
component life, and warranty coverage.
To reduce the risk of death, electric
shock, serious injury, or re, follow
basic precautions including the
following:
• Only qualied service technicians should
install and service the appliance.
• Wear appropriate personal protective
equipment (PPE) when servicing the
appliance.
• The appliance must be installed in
accordance with applicable national, state,
and local codes and regulations.
• Appliance is heavy. Use care when lifting
or positioning. Work in pairs when needed
to prevent injury or damage. Do not lift
using the top section or the doors/drawers.
• To reduce the risk of electric shock, do not
touch the plug with damp hands.
• Unplug the appliance before servicing.
• The appliance requires an independent
power supply of proper capacity. See the
nameplate for electrical specications.
Failure to use an independent power
supply of proper capacity can result in a
tripped breaker, blown fuse, damage to
existing wiring, or component failure. This
could lead to heat generation or re.
• THE APPLIANCE MUST BE
GROUNDED. The appliance is equipped
with a NEMA5-15 three-prong grounding
plug to reduce the risk of potential
shock hazards. It must be plugged into a
properly grounded, independent 3-prong
wall outlet. If the outlet is a 2-prong outlet,
it is your personal responsibility to have
a qualied electrician replace it with a
properly grounded, independent 3-prong
wall outlet. Do not remove the ground
prong from the power cord and do not use
an adapter plug. Failure to follow these
instructions may result in death, electric
shock, or re.
• Do not use an extension cord.
• Do not use an appliance with a damaged
power cord. The power cord should not be
altered, jerked, bundled, weighed down,
pinched, or tangled. Such actions could
result in electric shock or re. To unplug
the appliance, be sure to pull the plug, not
the cord, and do not jerk the cord.
• The GREEN ground wire in the factory-
installed power cord is connected to the
appliance. If it becomes necessary to
remove or replace the power cord, be
sure to connect the power cord's ground
wire.
• Do not splash, pour, or spray water
directly onto or into the appliance. This
might cause short circuit, electric shock,
corrosion, or failure.
• Do not make any alterations to the
appliance. Alterations could result in
electric shock, injury, re, or damage to
the appliance.
• The appliance is not intended for use by
persons (including children) with reduced
physical, sensory, or mental capabilities,
or lack of experience and knowledge,
unless they have been given supervision
or instruction concerning use of the
appliance by a person responsible for
their safety.

6
• Do not block air inlets or outlets, otherwise
cooling performance may be reduced.
• Do not tightly pack the cabinet. Allow some
space between items to ensure good air
ow. Also allow space between items and
interior surfaces.
• Do not put warm or hot foods in the cabinet.
Let them cool rst, or they will raise the
cabinet temperature and could deteriorate
other foods in the cabinet or overload the
appliance.
• Food storage and handling must comply with
applicable codes and regulations.
• All foods should be wrapped in plastic lm
or stored in sealed containers. Otherwise
foods may dry up, pass their smells onto
other foods, cause frost to develop, result in
poor appliance performance, or increase the
likelihood of cross-contamination. Certain
dressings and food ingredients, if not
stored in sealed containers, may accelerate
corrosion of the evaporator, resulting in
failure.
• Do not store items near air outlets.
Otherwise, items may freeze up and
crack or break causing a risk of injury or
contamination of other food.
WARNING, continued
• Children should be properly supervised
around the appliance.
• Do not climb, stand, or hang on the
appliance or doors/drawers or allow
children or animals to do so. Do not climb
into the appliance or allow children or
animals to do so. Death or serious injury
could occur or the appliance could be
damaged.
• Be careful not to pinch ngers when
opening and closing the doors/drawers or
rail cover (SR models) or when handling
food pans. Be careful when opening and
closing the doors/drawers or rail cover
when children are in the area.
• Open and close the doors/drawers and rail
cover (SR models) with care. Opening the
doors/drawers or rail cover too quickly or
forcefully may cause injury or damage to
the appliance or surrounding equipment.
• Do not use combustible spray or place
volatile or ammable substances in or
near the appliance. They might catch re.
• Keep the area around the appliance clean.
Dirt, dust, or insects in the appliance
could cause harm to individuals or
damage to the equipment.
• Do not throw anything onto the shelves
or load any single shelf with more than
120lb. (54.5 kg) of product. They might fall
off and cause injury.
• Do not load any single drawer with more
than 75 lb. (34 kg) of product. Depending
on the weight of product in the drawers,
secure the unit as necessary to prevent it
from overturning. Do not open more than
one drawer at a time.
• The appliance is designed only for
temporary storage of food. Employ
sanitary methods. Use for any other
purposes (for example, storage of
chemicals or medical supplies such
as vaccine and serum) could cause
deterioration of stored items.

7
WARNING, continued
Additional Warnings for SR Models
• The entire rail must always be covered
by rail dividers and pans (1/6 size, up
to 6"(15cm)deep). Otherwise, the
appliance will not cool properly.
• Use only 1/6 size pans up to 6"(15cm)
deep. Do not use damaged pans.
• Ingredients must be pre-chilled to 37°F
(3°C) or less before placing in rail.
• Keep the rail cover closed when not
actively preparing food.
• The rail is for keeping ingredients cool
while preparing food. If not actively
preparing food for a long period such
as overnight, seal pans with plastic
wrap in addition to closing the rail cover.
Depending on conditions, the cabinet
temperature setting may need to be
adjusted to prevent items from freezing.
Alternatively, seal ingredients and store
them in a refrigerator or freezer.
NOTICE
• Protect the oor when moving the
appliance to prevent damage to the oor.
• Keep ventilation openings, in the
appliance enclosure or in the built-in
structure, clear of obstruction. Do not
place anything on top of the appliance in
an undercounter installation. There must
be at least 1.5" (4 cm) overhead clearance
for proper ventilation. The factory-installed
rear bumpers must be in place to ensure
proper rear clearance. Blockage of airow
could negatively affect performance and
damage the appliance.
• Do not allow the appliance to bear any
outside weight.
• To prevent deformation or cracks, do not
spray insecticide onto the plastic parts or
let them come into contact with oil.
• To avoid damage to the gasket, use only
the door/drawer handle when opening
and closing.
• To avoid damage to the top seal, do not lift
the appliance by the top panel or remove
the top panel.
Additional Notice for SR Models
• Do not place anything on top of the rail
hood or rail cover and do not lift the
appliance by the rail hood or rail cover.
The rail hood and rail cover are not
designed to bear any outside weight.

8
I. Construction and Refrigeration Circuit Diagram
A. Construction
1. Solid Door Models
Compressor Condenser Fan Motor
Condenser
Rear Panel
Thermometer
Door
Door Gasket
Nameplate
• Evaporator
• Evaporator Fan
• Evaporator Fan Shroud
Control Module with Cabinet
Temperature Control Dial
Model Shown: UR27B
Model Shown: UR27B

9
2. Glass Door Models
Compressor Condenser Fan Motor
Condenser
Rear Panel
Thermometer
Door
Door Gasket
Nameplate
• Evaporator
• Evaporator Fan
• Evaporator Fan Shroud
Control Module with Cabinet
Temperature Control Dial
Model Shown: UR27B-GLP01
LED Driver
Channel
Model Shown: UR27B-GLP01
LED Lights

10
B. Refrigeration Circuit Diagram
Evaporator Fans
(1, 2, or 3 depending on model)
Evaporator
Compressor
Drier
Condenser Fan
Condenser
SR and UF/WF Models: Defrost Heater
Capillary Tube
Cabinet Thermistor
Defrost Thermistor
Condensate Pan

11
Red, Yellow, and Green LEDs Cycle
II. Sequence of Operation and Service Diagnosis
The steps in the sequence are as outlined below.
A. Sequence of Operation Flow Chart
1. UR/WR: Refrigerator
Legend: Comp-compressor ConFM-condenser fan motor CTh-cabinet thermistor DLT- defrost lockout timer DT- defrost timer (cumulative) DTh-defrost thermistor EvapFM-evaporator fan motor
Note:
a) 2-min. minimum Comp on timer starts when Comp energizes b) 2-min. minimum Comp off timer starts when Comp de-energizes c) 5-hr. cumulative compressor run-time defrost timer d) 5-min. minimum defrost time e) 55-min. maximum defrost time f) 1-hr. minimum between defrost cycles (DLT)
*
1. Startup/Cool Down
Comp energized ConFM energized EvapFM energized
5-hr. DT starts
Comp de-energized ConFM de-energized EvapFM de-energized
UR/WR - Refrigerator Sequence Flow Chart
2. Cool Down Achieved 4. Defrost
CTh above setpoint CTh cools to setpoint
CTh above
setpoint
Defrost Termination: 45°F (7.2°C) achieved or 55 min. maximum DT terminated.
CTh in control
1-hr. DLT terminates Evap. temp. at or below -4°F (-20°C) or 5-hr DT terminates 5-min. min. DT starts 55-min. max. DT starts Comp de-energized ConFM de-energized EvapFM energized
Defrost: Temperature or Time achieved.
Power on Yellow LED On (10-sec. Delay)
Green LED on Red and Yellow LEDs off
Evap. Temp. achieves 45°F (7.2°C) or 55-min. DT terminates, Defrost Terminated 1-hr. DLT starts 5-hr. DT starts
Comp energized ConFM energized EvapFM energized
*
DTh in control
5. Defrost Termination
DTh achieves -4°F(-20°C) or 5-hr. DT terminates
3. Cool Down Restarts
Red and Green LEDs on Yellow LED off
5-min. minimum and
55-min. maximum
DT starts
**
* * *
*
*

12
2. SR: Refrigerator
SR - Refrigerator Sequence Flow Chart
2. Cool Down Achieved
3. Cool Down Restarts
EvapFM energized Comp de-energized ConFM de-energized
4. Defrost
CTh above setpoint CTh cools to setpoint
CTh above
setpoint
Defrost Termination: 46°F (7.7°C) achieved or 45 min. backup defrost timer terminated.
CTh in control
1. Startup/Cool Down
Comp energized ConFM energized EvapFM energized 5-hr. DT starts
5-hr. DT terminates 5-min. minimum DT starts 45-min. maximum DT starts DH energized Comp de-energized ConFM de-energized EvapFM de-energized
Defrost: Time achieved. 5-hr. DT terminates
Power on Yellow LED On (10-sec. Delay)
Legend: Comp-compressor ConFM-condenser fan motor CTh-cabinet thermistor DH-defrost heater DT-defrost timer DTh-defrost thermistor EvapFM-evaporator fan motor
Note:
a) 2-min. minimum Comp on timer starts when Comp energizes b) 2-min. minimum Comp off timer starts when Comp de-energizes c) 5-hr. cumulative compressor run-time defrost timer d) 5-min. minimum defrost time e) 45-min. maximum defrost time
*
Green LED on Red and Yellow LEDs off
Evap. Temp. achieves 46°F (7.7°C) or 45 min. DT terminates DH de-energized Comp energized ConFM energized EvapFM energized
*
*
*
DTh in control
5. Defrost Termination
5-min. minimum and 45-min. maximum DT starts
Red, Yellow, and Green LEDs Cycle
*
*
Red and Green LEDs on Yellow LED off

13
3. UF/WF: Freezer
UF/WF - Freezer Sequence Flow Chart
Legend: Comp-compressor ConFM-condenser fan motor CTh-cabinet thermistor DH-defrost heater DLT-defrost lock-out timer DT-defrost timer DTh-defrost thermistor EvapFM-evaporator fan motor FDD-fan delay after defrost MH-mullion heater PH-perimeter heater
1. Startup/Cool Down 2. Cool Down Achieved
Comp energized ConFM energized EvapFM energized MH energized PH energized 5-hr. DT starts
CTh in control
4. Defrost
Comp de-energized ConFM de-energized EvapFM de-energized
MH de-energized PH de-energized
5. Defrost Termination
DTh in control
Green LED on Red and Yellow LEDs off
Defrost Termination: 55°F (°12.7C) achieved or 1 hr. backup defrost timer terminated.
1-hr. DLT terminates 5-hr. DT terminates or Evap. temp. at or below -31°F (-35°C) 5-min. minimum DT starts 1-hr. maximum DT starts DH energized Comp de-energized ConFM de-energized EvapFM de-energized MH de-energized PH de-energized
Note:
a) 2-min. minimum Comp on timer starts when Comp energizes b) 3-min. minimum Comp off timer starts when Comp de-energizes c) 5-min. minimum defrost time d) 1-hr. maximum defrost time e) 3-min. Comp/ConFM delay timer starts when defrost termination temperature is met (drip off time (DOT)) f) 1-hr. defrost lock-out time after defrost terminated (DLT) g) 3-min. EvapFM delay timer terminates or DTh reaches 10°F (-12°C) (FDD (fan delay after defrost), then evaporator fan motor energizes.
*
Evap. Temp. achieves 55°F (12.7°C) or 1-hr. DT terminates DH de-energized 3-min. DOT starts Comp energized ConFM energized MH energized PH energized
*
*
3-min. DOT terminates or Evap Temp. Achieves 10°F (-12°C) (FDD) 1-hr. DLT starts 5-hr. DT starts EvapFM energized
Red and Green LEDs on Yellow LED off
Power on Yellow LED On (10 sec. Delay)
Defrost: Temperature or Time achieved. DTh achieves -31°F(-35°C) or 5-hr. DT terminates
Red, Yellow, and Green LEDs Cycle
3. Cool Down Restarts
CTh above setpoint CTh cools to setpoint
CTh above
setpoint
*
6. Drip Off Time
* * * *
*
*
* *
5-min. minimum and
1-hr. maximum DT starts
3-min DOT Terminates

14
B. Service Diagnosis
DANGER
Risk of Fire or Explosion
Flammable Refrigerant Used
• Follow handling instructions carefully
in compliance with U.S. government
regulations.
• Do not use mechanical devices to defrost.
• Do not puncture refrigerant tubing. Risk
of re or explosion due to puncture
of refrigerant tubing; follow handling
instructions carefully.
• Component parts shall be replaced with
like components.
• Servicing shall be done by factory
authorized service personnel to minimize
the risk of possible ignition due to
incorrect parts or improper service.
• Consult instruction manual/service manual
before attempting to install or service this
product. All safety precautions must be
followed.
• Dispose of properly in accordance with
federal or local regulations.
• Do not place any potential ignition sources
in or near the appliance.
Risque De Feu Ou D'Explosion
Le Frigorigène Est Inammable
• Suivre attentivement les instructions
de manipulation conformément à la
réglementation gouvernementale.
• Ne pas utiliser d'appareils mécaniques
pour dégivrer le réfrigérateur.
• Ne pas perforer la tubulure contenant le
frigorigène. Risque de feu ou d'explosion
si la tubulure contenant le frigorigène
est perforée; suivre les instructions de
manutention avec soin.
• Les pièces des composants doivent être
remplacées par des pièces et accessoires
équivalents.
• L’entretien doit être effectué par le
personnel de service autorisé par le
fabricant an de minimiser les risques
d’inammation attribuables à l’installation
d’une pièce inadéquate ou à la mauvaise
exécution du service.
• Consulter le manuel du propriétaire/
guide de réparation avant de tenter une
réparation. Toutes les mesures de sécurité
doivent être respectées.
• Éliminer conformément aux règlements
fédéraux ou locaux.
• Ne placez aucune source d’inammation
potentielle dans ou près de l’appareil.
WARNING
• The appliance should be diagnosed and repaired only by qualied service
personnel to reduce the risk of death, electric shock, serious injury, or re.
• Wear appropriate personal protective equipment (PPE) when servicing the
appliance.
• Risk of electric shock. Use extreme caution and exercise safe electrical practices.
• Moving parts (e.g., fan blade) can crush and cut. Keep hands clear.
• Appliance is heavy. Use care when lifting or positioning. Work in pairs when
needed to prevent injury or damage.
• Make sure all food zones are clean after the appliance is serviced.

15
1. Diagnostic Procedures
The diagnostic procedure is a sequence check that allows you to diagnose the electrical
system and components. Before proceeding, check for correct installation and proper
voltage per nameplate.
See the table for default cabinet temperature control dial settings.
Model Default Cabinet Temperature
Control Dial Setting
Approximate Default Temperature
UR/WR - Undercounter/Worktop 5 Refrigerator: 34°F (1°C)
SR - Prep Table 5 Refrigerator: 34°F (1°C)
UF/WF - Undercounter/Worktop 7 Freezer: -5°F (-21°C)
The diagnostic procedure is a sequence check that allows you to diagnose the electrical
system and components. Before proceeding, check for correct installation and proper
voltage per nameplate.
Conrm that the appliance location meets factory requirements:
• This appliance is not intended for outdoor use. Normal operating ambient
temperature:
– All UR/WR and Solid Door UF/WF 45°F to 100°F (7°C to 38°C)
– SR 45°F to 86°F (7°C to 30°C)
– UF Glass Door 45°F to 80°F (7°C to 27°C).
• The appliance should not be located next to ovens, grills, or other high heat
producing equipment. Check CM using the steps in "II.C. Control Module Check."
Note: • When checking voltage (115VAC), always choose a neutral white (W) wire to
establish a good neutral connection.
• Control module has high and low voltage protection. If off on either protection,
no LED is visible and all components are off.
High Voltage: 140VAC
Low Voltage: 90VAC
• There is a 2 min. minimum compressor on time for all models and a 2-min.
minimum compressor off time for UR/WR and SR and a 3-min. minimum
compressor off time for UF/WF.
• The control module incorporates LEDs
to identify sequence of operation.
Reference the table below to assist in
the diagnostic process.
CONTROL MODULE LED OPERATION
LEDs LED OPERATION
R Y G
XX
X
5-SEC. DELAY
X
X
SYSTEM ON
X
X
CTh SATISFIED; SYSTEM OFF
X2-MIN. ON/OFF DELAY
XDEFROST/DTh FAULT
SYSTEM OFF
XCTh FAULT
LED OPERATION LEGEND
CYCLING CTh - CABINET THERMISTOR
FLASHING DTh - DEFROST THERMISTOR
ON
X OFF

16
1) Unplug the appliance from the electrical outlet.
2) Remove the CM mounting bracket and place the CM in a place where the LEDs are
visible.
3) Plug the appliance back into the electrical outlet. If appliance was in defrost when
power supply was disconnected, defrost is terminated and normal cooling cycle begins.
4) Startup/Cool Down–All 3 LEDs ash on then off, then a solid yellow LED turns on for
10 sec., yellow LED turns off and solid green LED turns on (normal cooling cycle).
CTh Temperature above setpoint, Comp, ConFM, EvapFM, PH (UF/WF only), and
MH (UF/WF only) energize. 2-min. Comp on timer and 5-hr. DT starts.
a) CTh Diagnosis: If CTh fails, green and yellow LEDs ash on the CM. Conrm CTh
is properly connected to CM. Check Ohm reading of CTh. See "II.D. Thermistor
Check." Replace as needed.
b) CM Diagnosis: Conrm green LED is solid. If not, conrm CTh is above setpoint.
Next, check for 115VAC between CM Live In black (BK) wire and a neutral white
(W) wire. If 115VAC is not present, check power cord connections and breaker/fuse.
Conrm wiring connections are secure for both CM Live In black (BK) and a neutral
white (W) wire. If 115VAC is present, CTh is above setpoint, and CM green LED is
not on, replace CM.
c) Comp/ConFM Diagnosis: Check that Comp and ConFM energize. Next, check for
115VAC at CM Comp violet (V) wire to a neutral white (W) wire. If 115VAC is not
present at CM Comp violet (V) to a neutral white (W) wire, check CTh status. See
"II.D. Thermistor Check." If CTh ohm reading is in proper range, replace CM.
Comp: If 115VAC is present, check Comp external overload, start or run cap (if
applicable), PTC relay or start relay, and Comp motor windings. Replace as needed.
ConFM: If 115VAC is present, check fan blade for binding, then check ConFM motor
windings. If Comp, ConFM, and EvapFM are energized and the cabinet does not
cool down, check for a restriction in the refrigeration circuit, low refrigerant charge,
or inefficient Comp.
d) EvapFM Diagnosis: Check that EvapFM(s) energize. If not, check for 115VAC at
CM Aux 1 black-smooth (BK-SM) wire to neutral white (W) wire. If 115VAC is not
present, replace CM. If 115VAC is present, check fan blades for binding, then check
EvapFM motor windings.
e) PH and MH Diagnosis (UF/WF only): PH and MH follow Comp operation. When
Comp is energized, PH and MH are energized. If 115VAC is present, check amp
draw of PH and MH. If an amp reading is not present, check the continuity of PH
and MH. If defective, replace PH or MH.
f) Glass Door Cabinet LEDs Diagnosis: LED(s) are activated by CLS. If CLS is
engaged and LED(s) fail to turn on, check for 115VAC at both CLS (Y) wires to a
neutral white (W) wire. If 115VAC is present on one end and not the other, check
CLS continuity. If open replace CLS. If CLS is closed and 115VAC is present on both
CLS (Y) wires to a neutral (W), check for 24VDC at DCD black (BK) wire to DCD red
(R) wire. If 24VDC is not present, check continuity of DCD driver. If open, replace
DCD driver. If 24VDC is present and LED(s) are not on, check wiring harness and
wiring connections from DCD to LED(s). If connections are good and LED(s) are not
on, replace CM.

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5) Cool Down Achieved–CTh reaches setpoint temperature.
All Models: Comp and ConFM de-energize.
UR/WR and UF/WF: EvapFM de-energize.
SR: EvapFM continues.
Diagnosis: If temperature setpoint achieved and Comp, ConFM, and EvapFM does not
de-energize (except SR), check CTh continuity. See "II.D. Thermistor Check."
If CTh is defective, replace. If CTh is good and either the Comp, ConFM, or EvapFM
continue, replace CM. SR: If EvapFM de-energizes, check for 115VAC at CM Aux 1
black-smooth (BK-SM) wire to neutral white (W) wire. If 115VAC is not present, replace
CM. If 115VAC is present, check fan blades for binding, then check EvapFM motor
windings.
6) Defrost–Manual, temperature, and time-initiated defrost with temperature-terminated
defrost. Defrost has a 5-min. minimum time and a 55-min. maximum time on UR/WR,
a 1-hr. maximum time on UF/WF, and a 45-min. maximum time on SR.
1a) Manual-Initiation (All): Unplug the appliance from the electrical outlet, then move
the CTCD to the off position. Plug the appliance back in to the electrical outlet. The
green, yellow, and red LED turn on. Rotate the CTCD clockwise to position 4 (green
and red LED turn off, yellow LED remains on), move counter-clockwise to position 2
(yellow LED turns off and red LED turns on), move back clockwise again to position
8 (red LED remains on and green LED turns on). Defrost initiates.
Note: Once at the number position, conrm the appropriate LEDs turn off and on.
If not, move the CTCD back and forth until the LED turns on. Once the LED is on,
move to the next position.
1b) Temperature Initiation:
(1) UR/WR: DTh is at or below -4°F (-20°C), defrost starts. CM red and green LED
turn on. If energized, Comp and ConFM de-energize. EvapFM continues.
(2) SR: No temperature initiation. Time only.
(3) UF/WF: DTh at or below -31°F (-35°C), defrost starts. CM red and green LED
turn on. If energized, Comp, ConFM, EvapFM, PH, and MH de-energize.
DH energizes. 5-min. minimum DT starts and 1-hr. maximum DT starts.
1c) Time Initiation (All):
5-hr. cumulative compressor run timer terminates, defrost starts.
(1) UR/WR: Comp and ConFM de-energize. EvapFM continues. 5-min. minimum DT
starts and 55-min. maximum DT starts.
(2) SR: Comp, ConFM, and EvapFM de-energize. DH energizes. 5-min. minimum DT
starts and 45-min. maximum DT starts.
(3) UF/WF: Comp, ConFM, EvapFM, PH, and MH de-energize.
DH energizes. 5-min. minimum DT starts and 1-hr. maximum DT starts.
Note: There is a 1-hr. defrost lock-out after a defrost cycle terminates. This may be
bypassed by initiating a manual defrost or unplugging and plugging back in to
the electrical outlet.

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2a) Manually-Terminated: Set the CTCD to the off position, then back to original setting
or unplugging and plugging back in to the electrical outlet. Defrost terminated.
2b) Temperature or Time Terminated:
(1) UR/WR: 45°F (7.2°C) achieved or 55-min. backup DT terminates. If CTh calling
for cooling, Comp and ConFM energize. EvapFM continues.
(2) SR: 46°F (7.7°C) achieved or 45-min. backup DT terminates.
DH de-energizes. Comp, ConFM, and EvapFM energize.
(3) UF/WF: 55°F (12.7°C) achieved or 1-hr. backup DT terminates.
DH de-energizes. 3-min. DOT starts. 3-min. DOT terminates. If CTh calling for
cooling, Comp, ConFM, PH, and MH energize. Once evaporator temperature
achieves 10°F (-12.2°C) or 3-min. EvapFM delay timer terminates, EvapFM
energizes.
Defrost Diagnosis
1) Manual Initiated: Unplug the appliance from the electrical outlet, then move the
CTCD to the off position. Plug the appliance back in to the electrical outlet. The
green, yellow, and red LED turn on. Rotate the CTCD clockwise to position 4 (green
and red LED turn off, yellow LED remains on), move counter-clockwise to position 2
(yellow LED turns off and red LED turns on), move back clockwise again to position
8 (red LED remains on and green LED turns on). Defrost initiates. Note: Once at
the number position, conrm the appropriate LEDs turn off and on. If not, move the
CTCD back and forth until the LED turns on. Once the LED is on, move to the next
position. After several attempts and the LEDs do not turn on and off as listed above,
replace the CM. If defrost does not initiate after all the LEDs properly turn on and
off, replace the CM. Once initiated, see component diagnosis below in "3) Time
Initiated."
2) Temperature Initiated:
a) UR/WR: Has 1-hr. DLT terminated? Has DTh cooled to -4°F (-20°C) or lower?
b) SR: Has DTh cooled to -4°F (-20°C) or lower?
a) UF/WF: Has 1-hr. DLT terminated? Has DTh cooled to -31°F (-35°C) or lower?
(1) DTh Diagnosis: If DTh has cooled to proper temperature, conrm DTh status.
See "II.D. Thermistor Check."
(2) CM Diagnosis: Check that CM red and green LEDs turn on. If not, and DTh ohm
reading is in proper range, replace CM.
3) Time Initiated: 5-hr. cumulative compressor run timer terminates.
(1) CM Diagnosis: Conrm green and yellow LEDs turn on. If not, After attempting
CTCD sequence several times and defrost still not initiated, wait 1 to 2 min. and
repeat process. If defrost cycle still not activated, replace CM as needed.
(2) Comp and ConFM Diagnosis: Conrm Comp and ConFM de-energize.
If not, check for 115VAC at CM Comp violet (V) wire to a neutral white (W) wire.
If 115VAC is present, Check DTh continuity. See "II.D. Thermistor Check."
Replace as needed. If DTh conrmed, replace CM.

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(3) EvapFM Diagnosis
UR/WR: EvapFM continues. If not, check for 115VAC at CM
AUX 1 black-smooth (BK-SM) wire to a neutral white (W). If 115VAC is not
present, replace CM.
SR and UF/WF: Conrm EvapFM de-energizes. If not, check for 115VAC at
CM AUX 1 black-smooth (BK-SM) to a neutral white (W). If 115VAC is present,
conrm Comp and ConFM de-energized. Next, check DTh continuity. See "II.D.
Thermistor Check." Replace as needed. If DTh conrmed, replace CM.
(4) DH Diagnosis (SR and UF/WF): Conrm DH energizes. Check for 115VAC at
CM AUX 2 black (BK) wire to a neutral white (W). If 115VAC is present, conrm
Comp, ConFM, and EvapFM de-energized. Next, check DTh continuity. See "II.D.
Thermistor Check." Replace as needed. If DTh conrmed, replace CM.
2) Defrost Termination
Manually Terminated Defrost: Set the CTCD to the off position, then back to
original setting or unplugging and plugging back in to the electrical outlet. Defrost
terminated. If not, replace CM.
Temperature/Time Terminated Defrost
a) UR/WR: DTh warms to 45°F (7.2°C). Conrm continuity of DTh.
See "II.D. Thermistor Check." Replace as needed. If DTh conrmed, replace CM.
Once defrost termination achieved, EvapFM continues. Comp and ConFM energize.
If not, see "4) Startup/Cool down" above.
b) SR: DTh warms to 46°F (7.7°C). DH de-energizes. Conrm continuity of DTh. See
"II.D. Thermistor Check." Replace as needed. If DTh is good and DH continues after
DTh achieves 46°F (7.7°C), replace CM. Comp, ConFM, and EvapFM energize. If
not, see "4) Startup/Cool down" above.
c) UF/WF: DTh warms to 55°F (12.7°C) DH de-energizes. Conrm continuity of DTh.
See "II.D. Thermistor Check." Replace as needed. If DTh is good and DH continues
after DTh achieves 55°F (12.7°C), replace CM. 3-min. DOT starts. 3-min. DOT
terminates. If CTh calling for cooling, Comp, ConFM, PH, and MH energize. Once
evaporator temperature achieves 10°F (-12.2°C) or 3-min. EvapFM delay timer
terminates, EvapFM energizes. If not, see "4) Startup/Cool down" above.
Legend: Comp–compressor; ConFM–condenser fan motor; CLS–cabinet light switch;
CM–control module; CTCD–cabinet temperature control dial; CTh–cabinet
thermistor; DH–defrost heater; DLT–defrost lock-out timer; DST–defrost safety
thermostat; DT–defrost timer; DTh–defrost thermistor; EvapFM–evaporator fan
motor; HPS–high-pressure switch; MH–mullion heater; PH–perimeterheater

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C. Control Module Check
1. Control Module
Before replacing a CM that does not show a visible defect and that you suspect is bad,
conduct the following check procedure. This procedure will help you verify your diagnosis.
Always choose a neutral white (W) wire to establish a good power supply and neutral
connection to CM. Check that 115VAC is present between CM Live In black (BK) wire
and CM Neutral white (W) wire. Conrm defrost and cabinet thermistors are connected.
Control Module
Cabinet Thermometer
(located on shelf)
Cabinet Temperature
Control Dial
Setting Position
Cabinet Temperature Control Dial
(Shown if "OFF" Position)
Control Dial
Setting Position
Control Dial
Cabinet Temperature
Control Dial
Setting Position
Cabinet Temperature
Control Dial
Setting Position
Fig. 1
Compressor (V)
Evaporator Fan
Motor (BK-SM)
Defrost Heater (BK-SM)
Neutral (W)
Power Supply (BK)
PRB 2
Defrost
Thermistor
PRB 1
Cabinet
Thermistor
Red LED
Yellow LED
Green LED