Dometic NDA1402, NDE1402 Service Manual

DIAGNOSTIC SERVICE MANUAL

NDA1402 & NDE1402

WITH AUTO DEFROST

USA
Dometic, LLC.
2320 Industrial Parkway
Elkhart, IN. 46516
574-294-2511

CANADA
Dometic, LLC.
46 Zatonski Unit 3
Brantford, Ontario
CANADA N3T 5L8
519-720-9578

Form No. 3312260.000 06/08
©2008 Dometic, LLC.
LaGrange, IN. 46761 USA

3

foreword

This service manual is the result of the dedica­tion of Dometic, LLC technical staff and its en­gineers in giving service people the necessary
instruction for making accurate analyses of cer­tain conditions. Provided is a diagnostic chart

leading a qualied mechanic into the service

manual pages to locate and solve symptoms
which may occur. Dometic, LLC has continued
its commitment in providing service people with
this, the most up-to-date information about ser­vicing Dometic RV accessories.

Safety InStructIonS

This manual has safety information and instruc­tions to help users eliminate or reduce the risk
of accidents and injuries.

recognIze Safety InformatIon

This is the safety-alert symbol. When you see this
symbol in this manual, be alert to the potential
for personal injury.

Follow recommended precautions and safe op­erating instructions.

underStand SIgnal WordS

A signal word, WarnIng OR cautIon is used
with the safety-alert symbol. They give the level
of risk for potential injury.

Indicates a potentially hazard-

ous situation which, if not avoided, could result
in death or serious injury.

Indicates a potentially hazard-

ous situation which, if not avoided may result in
minor or moderate injury.

When used without the safety

alert symbol indicates, a potentially hazardous
situation which, if not avoided may result in prop­erty damage.

Read and follow all safety information and in­structions.

32

contentS

Page no.

DIAGNOSTIC FLOW CHART..........................................................................6

SectIon 1

oVerVIeW/oPeratIon

Refrigerator Overview/Operation..........................................................................9

SectIon 2

ac Voltage

AC Voltage Requirements...................................................................................12

SectIon 3

ac comPonentS

3.1 Heating Element.........................................................................................12

3.2 Interface Module.........................................................................................13

3.3 AC Sensing.................................................................................................14

SectIon 4

dc Voltage

4.1 DC Voltage Requirements ....................................................................... ..14

4.2 Grounds......................................................................................................14

SectIon 5

dc comPonentS

5.1 Door Switches and lamps.........................................................................

5.2 Temperature Sensors................................................................................

5.3 Low Ambient Control.................................................................................

5.4 Frame Heater............................................................................................

5.5 Interior Fans..............................................................................................

5.6 Thermo Fuse..............................................................................................

5.7 Flame Sensing...........................................................................................

5.8 Ignition Control Module..............................................................................

5.9 Electrode....................................................................................................

5.10 High Voltage Cable....................................................................................

5.11 Solenoid (Gas)..........................................................................................

5.12 Front Display Panel...................................................................................

5.13 Lower Board.............................................................................................

5.14 Fuses........................................................................................................

14
15
15
15
16
16
16
17
17
17
18
18
21
21

SectIon 6

lP gaS

LP Gas Requirements.......................................................................................22

3

5

contentS

Page no.

SectIon 7

lP gaS comPonentS

7.1 Manual Gas Shutoff Valve........................................................................22

7.2 Orice.......................................................................................................22

7.3 Burner.......................................................................................................23

7.4 Flue Bafe................................................................................................23

7.5 Flue Cap..................................................................................................23

7.6 Flue Tube.................................................................................................23

SectIon 8

coolIng unIt

8.1 Cooling Unit......................................................... ....................................23

8.2 Ventilation.................................................................................................25

8.3 Ventilator Fans.........................................................................................27

8.4 Leveling....................................................................................................27

8.5 Food Storage...........................................................................................27

8.6 Ambient Temperature...............................................................................27

SectIon 9

froSt

9.1 Door Seals...............................................................................................27

9.2 Interior Liner Seal to Frame.....................................................................28

9.3 Drain Tube...............................................................................................29

9.4 Wall Entrances.........................................................................................29

9.5 Auxiliary Defrost Fan................................................................................29

9.6 High Humidity...........................................................................................29

9.7 Door Position...........................................................................................29

SectIon 10

defroStIng

10.1 Real Time Clock.....................................................................................30

10.2 Automatic Defrosting..............................................................................30

10.3 Manual Defrosting..................................................................................31

10.4 Drying Function......................................................................................31

10.5 Freezer Defrost Heating Element..........................................................31

10.6 Fresh Food Defrost Heating Element....................................................32

10.7 Drain Tube/Tray Defrost Heating Element.............................................32

54

contentS

Page no.

SectIon 11

trouBleSHootIng

11.1 Status Messages.....................................................................................33

11.2 Error Codes.............................................................................................34

11.3 Service Mode..........................................................................................36

SectIon 12

Ice maKer

12.1 Operation............................................. ..............................................38

12.2 Mold Heater...........................................................................................38

12.3 Ice Ejector..............................................................................................38

12.4 Mold Thermostat....................................................................................39

12.5 Shutoff Arm............................................................................................39

12.6 Mold Switches......................................................................................39

12.7 Timing Motor..........................................................................................39

12.8 Water Valve...........................................................................................39

12.9 Ice Maker Replacement........................................................................40

12.10 Water Fill Adjustment............................................................................40

12.11 Fill Tube................................................................................................40

12.12 Water Supply........................................................................................41

12.13 Wiring...................................................................................................42

SectIon 13

door dISPenSer

13.1 Operation................................................................................................46

13.2 Auger.......................................................................................................46

13.3 Solenoid.............................................................................................. .. . .. 47

13.4 Ice Shutter...............................................................................................47

13.5 Water Dispenser......................................................................................48

13.6 Door Mechanism and Display Panel........................................................48

SectIon 14

WIrIng

14.1 Internal Wiring........................................................................................48

14.2 External Wiring.......................................................................................48

14.3 Wiring Schematics..................................................................................48

SectIon 15

mIScellaneouS

15.1 Thermistors............................................................................................49

5

7

This service manual will address the most common system problems associated with the NDA 1402 and NDE 1402 refrig­erators supplied by Dometic, LLC. Our intent is to provide you with a guideline of checks to make, should you encounter
one of the following symptoms.

SYMPTOM

1. No operation - no panel lights

2. No operation - has panel lights

3. No AC operation - operates on gas
mode

CAUSE

Operation
DC Volts
Fuses
Wiring
Front Display Panel
Lower Circuit Board

Operation
DC Volts
Temperature Sensors
Wiring
Lower Circuit Board

Operation
AC Volts
Fuses
Heating Elements
Wiring
Lower Circuit Board

SECTION & PAGE

1, page 09
4, page 14
5, page 21
14, page 48
5, page 18
5, page 21

1, page 09
4, page 14
5, page 15
14, page 48
5, page 21

1, page 09
2, page 12
5, page 21
3, page 12
14, page 48
5, page 21

4. No Gas operation - operates on AC

mode

5. Insufcient cooling on all modes.

6. Insufcient cooling on AC - cools prop-

erly on gas mode.

Operation
LP Gas
Manual Gas Valve
Ignition Control Module
High Voltage Cable
Electrode
Solenoid (Gas)
Wiring
Lower Circuit Board

Ventilation
Ventilator Fans
Leveling
Ambient Temperature
Drain Tube
Wall Entrances
Temperature Sensors
Cooling Unit

AC Volts
Heating Elements
Lower Circuit Board

1, page 09
6, page 22
7, page 22
5, page 17
5, page 17
5, page 17
5, page 18
14, page 48
5, page 21

8, page 25
8, page 27
8, page 27
8, page 27
9, page 29
9, page 29
5, page 15
8, page 23

2, page 12
3, page 12
5, page 21

76

This service manual will address the most common system problems associated with the NDA 1402 and NDE 1402 refrig­erators supplied by Dometic, LLC. Our intent is to provide you with a guideline of checks to make, should you encounter
one of the following symptoms.

SYMPTOM

7. Insufcient cooling on Gas - cools

properly on AC mode.

8. Water on frame

9. Rapid formation of frost

CAUSE

LP Gas

Orice
Flue Bafe

Flue Tube
Burner
Lower Circuit Board

Interior Liner Seal to Frame
Wall Entrances
High Humidity
Frame Heater

Food Storage
Interior Liner Seal to Frame
High Humidity
Door Seals
Drain Tube
Wall Entrances
Auxiliary Defrost Fan

SECTION & PAGE

6, page 22
7, page 22
7, page 23
7, page 23
7, page 23
5, page 21

9, page 28
9, page 29
9, page 29
5, page 15

8, page 27
9, page 28
9, page 29
9, page 27
9, page 29
9, page 29
9, page 29

10. Unit is not defrosting

11. Frost around drain tube

12. General Frost (freezer)

13. General Frost (fresh food)

Real Time Clock
DC Volts
Temperature Sensors
Freezer Defrost Heating Element
Drain Tube/Tray Heating Element
Fresh Food Heating Element

Drain Tube orice is too Small

Drain Tube/Tray Heating Element
Wall Entrances

Door Seals
Interior Liner Seal to Frame
Wall Entrances
Drain Hose
Freezer Defrost Heating Element
Drain Tube/Tray Heating Element

Door Seals
Interior Liner Seal to Frame
Wall Entrances
Drain Hose
Fresh Food Heating Element
Drain Tube/Tray Heating Element

10, page 30
4, page 14
5, page 15
10, page 31
10, page 32
10, page 32

9, page 29
10, page 32
9, page 29

9, page 27
9, page 28
9, page 29
9, page 29
10, page 31
10, page 32

9, page 27
9, page 28
9, page 29
9, page 29
10, page 32
10, page 32

7

9

This service manual will address the most common system problems associated with the NDA 1402 and NDE 1402 refrig­erators supplied by Dometic, LLC. Our intent is to provide you with a guideline of checks to make, should you encounter
one of the following symptoms.

SYMPTOM

14. Ice maker fails to start

15. Not making enough ice

16. Ejector blades frozen into ice

17. Ice around ice maker

18. No ice or water at the dispenser

CAUSE

Operation
Mold Thermostat
Shutoff Arm
Water Valve
Interface Module

Operation
Mold thermostat

Water Fill Adjustment
Water Supply
Water Valve

Water Fill Adjustment
Water Supply
Fill Tube

Operation
Lock Out Feature
Freezer Door is Open
Door Mechanism and Display

Panel

Interface Module

SECTION & PAGE

12, page 38
12, page 39
12, page 39
12, page 39
3, page 13

12, page 38
12, page 39

12, page 40
12, page 41
12, page 39

12, page 40
12, page 41
12, page 40

13, page 46
13, page 46
13, page 46
13, page 48

3, page 13

19. No ice at the dispenser

20. No “cubed” ice at the dispenser

21. Water/Condensation at the dispenser

Operation
Lock Out Feature
Freezer Door is Open
Door Mechanism and Display

Panel
Auger
Interface Module

Operation
Door Mechanism and Display

Panel
Solenoid
Interface Module

Water Fill Adjustment
Ice Shutter
High Humidity

13, page 46
13, page 46
13, page 46
13, page 48

13, page 46
3, page 13

13, page 46
13, page 48

13, page 47
3, page 13

12, page 40
13, page 47
9, page 29

98

SectIon 1

uSIng tHe control featureS

refrIgerator oVerVIeW

aBSorPtIon coolIng SyStem

In an absorption refrigerator system, ammonia is liqueed

in the nned condenser coil at the top rear of the refrig-

erator. The liquid ammonia then ows into the evaporator

(inside the freezer section) and is exposed to a circulat-

ing ow of hydrogen gas, which causes the ammonia to

evaporate, creating a cold condition in the freezer. When

starting this refrigerator for the very rst time, the cooling

cycle may require up to four hours of running time be­fore the cooling unit is fully operational. The tubing in the

evaporator section is specically sloped to provide a con-

tinuous movement of liquid ammonia, owing downward

by gravity through this section.

ImPortance of leVelIng

Leveling is one of the requirements for proper operation
with absorption refrigerators. To ensure proper leveling
the vehicle needs to be leveled so it is comfortable to live

in (no noticeable sloping of oor or walls). Any time the

vehicle is parked for several hours with the refrigerator
operating, the vehicle should be leveled to prevent this
loss of cooling. If the refrigerator is operated when it is
not level and the vehicle is not moving, liquid ammonia
will accumulate in sections of the evaporator tubing. This
will slow the circulation of hydrogen and ammonia gas, or
in severe cases, completely block it, resulting in a loss of
cooling. When the vehicle is moving, the leveling is not
critical, as the rolling and pitching movement of the ve­hicle will pass to either side of level, keeping the liquid
ammonia from accumulating in the evaporator tubing.

automatIc defroStIng control SyS­tem

This refrigerator is equipped with an automatic defrost­ing control system. The defrost system will automatical­ly carry out a defrost of the frozen food and fresh food
compartments once every 24 hours. To be able to con­trol the performance of the defrost intervals the system is
equipped with a built in real time clock. The clock has to
be set to local time at the very rst start up of the refrigera­tor or when the 12 volt DC supply has been disconnected
for a long period of time. A message on the LED display
panel will alert when the clock needs to be set. It is also
recommended to reset the clock when entering different
time zones.

modeS of coolIng

nda1402: This refrigerator is equipped with an automatic

energy selector system which automatically selects the
most suitable energy source that is available, either 120
volt AC or LP gas operation. The system can be set by the
user to be fully automatic, or to operate on LP gas only.

nea1402: All-electric operation.

NEA1402

1

1

1. ON/OFF button.
Press this button to turn the refrigerator on and off.

2. STORE button. (NEA1402)
AUTO/STORE button. (NDA1402)
Combined energy mode selection and store button.

3. LED display panel.

4. SET button.
Combined temperature range and real time clock ad-
justment.

2

2

3

3

4

NDA1402

4

led dISPlay Panel

The LED panel displays
temperatures in the refrig­erator, current modes of
operation and other useful
status messages.

The displayed temperature values reect the most prob­able temperature of the food in the two compartments. A
delay function prevents rapid changes due to door open­ings etc.

Panel Indications:

•

The most probable temperature of food in the fro­zen food compartment.
The most probable temperature of food in the •
fresh food compartment.
AUTO mode indication (NDA1402)•
AC operation indication.•
GAS operation indication (NDA1402)•
Thermostat setting indication (temporary during •
setting).
Real time clock/ PM indication (temporary during •
setting).
Various status and error messages.•

Store functIon

When setting the real time clock as well as the thermostat,
the desired setting is stored automatically after 5 sec. of
inactivity or by pressing the STORE button.

9

11

oPeratIon

Before starting the refrigerator, check that all the manual
gas valves are in the “ON” position. DO NOT forget the
manual shutoff valve on the rear of the refrigerator. The
NDA1402 model refrigerator is equipped with a control
system which can be set to automatically select either 120
volt AC or LP gas operation (AUTO mode), or if desired
LP gas only (GAS mode). The NDE1402 model refrigera­tor is an all electric 120 volt AC operation.

most lP gas appliances used in recreational
vehicles are vented to the outside of the ve­hicle. When parked close to a gasoline pump
or traveling through tunnels, it is possible
that the gasoline fumes could enter this type

of appliance and ignite from the burner ame,

cauSIng a fIre or an eXPloSIon.

for your Safety, when refueling or trav­eling through tunnels, shut off all lP gas ap­pliances which are vented to the outside.

deScrIPtIon of oPeratIng modeS
auto mode

When operating in the AUTO mode, the AUTO mode
indicator dot is lit. The control system will automatically
select between AC and GAS operation with AC having
priority over GAS. (An indicator dot will be lit to inform of
the energy source selected). If the control system is op­erating with AC energy and it then becomes unavailable,
the system will automatically switch to GAS. As soon as
AC becomes available again the control will switch back
to AC operation.

gas operation (120 volts AC is not available). The con­trol system will activate the ignition system and will make
three attempts to light the burner for a period of approxi­mately 45 seconds with two minutes rest (purge) interval.
If unsuccessful, “ch LP” will be displayed. To restart an
ignition attempt with “ch LP” in the display turn the unit off,
wait a few seconds and turn back on. The control system
will attempt a new ignition sequence. If 120 volts AC be­comes available while “ch LP” is displayed, the refrigera­tor will operate on AC but the “ch LP” will not turn off until
the main power ON/OFF button is pressed to the “OFF”
then “ON” position.

automatIc energy Selector control
SyStem

The NDA1402 model is equipped with an automatic ener­gy selector control system. The user turns the refrigerator
on and selects the desired temperature and then, the con­trol system selects the most suitable energy source avail­able (either 120 volt AC or LP gas operation). The system
can be set by the user to be fully automatic (AUTO mode
ON) or to operate on LP gas only (AUTO mode OFF).

The NDE1402 model is an all electric operation.

Press AUTO/STORE button to select AUTO mode opera­tion or to chose LP-gas mode of operation only.

modeS of oPeratIon (auto) & (gaS)

When the refrigerator is in the AUTO mode, it automati-

cally uses the most efcient energy source that is avail-

able for operation. Should a more efcient energy source

become available during operation, the refrigerator will
change from the current energy source to the more ef-

cient energy source as follows:

gaS mode

When operating in the GAS mode, the AUTO indication
dot will be off and the GAS indication dot is lit. This mode
provides LP gas operation only. The control system will
activate the ignition system and will make three attempts
to light the burner for a period of approximately 45 sec­onds with two minutes rest (purge) interval after each trial.
If unsuccessful, “ch LP” will be displayed. To restart GAS
Operation, press the main power ON/OFF button to the
“OFF” and then “ON” position. The control system will at­tempt a new ignition sequence. If the refrigerator has not
been used for a long time or the LP tanks have just been

relled, air may be trapped in the supply lines. To purge

the air from the lines may require resetting the main power
ON/OFF button three or four times. If repeated attempts
fail to start the LP gas operation, check to make sure that
the LP gas supply tanks are not empty and all manual
shutoff valves in the lines are turned on.

to Shut off the refrigerator

The refrigerator may be shut off while in any mode of
operation by pressing the main power ON/OFF button
to the “OFF” position. This shuts off all DC power to the
control system including the interior light.

•

AC operation (if 120 volt AC is available). AC op­eration is only possible in AUTO mode.
GAS operation (if 120 volt AC is not available).•

GAS mode (manual LP gas operation)

When the AUTO mode is turned off, the refrigerator
uses gas as an energy source - even if AC is avail­able.

1110

Start uP

tHermoStat SettIng

NDE1402:

Turn on the refrigerator by pressing the ON/OFF but­ton.

NDA1402:

fIre Hazard. If the refrigerator has not
been used for some time, and before light­ing the gas burner. check that the gas path
between the burner jet and the burner tube
has not been obstructed. failure to heed

this warning could cause a re resulting in

death, severe personal injury and property
damage.

•

Before turning on the refrigerator, verify that all the
manual gas valves, including the manual shut off
valve, are in the “ON” position.

•

Turn on the refrigerator by pressing the ON/OFF but­ton.

The freezer and the fresh food compartment tempera­tures are controlled separately and independently of each
other, based on the actual air temperature in each com­partment.

•

The freezer setting is pre-set (can not be changed) to
be approx. 0°F (-18°C) when running on AC. If run­ning on GAS the pre-set temperature is approx. 7°F
(-14°C).

•

The fresh food compartment can be set in 5 different
positions (1-5) where 5 is the coldest setting which
gives a fresh food temperature of approx. 33°F (0°C).
Setting 3 gives a temperature of approx. 37°F (3°C).

NEA1402

NDA1402

real tIme clocK

NEA1402

PM INDICATION

PM INDICATION

If the real time clock has to be set, the LED panel will

show ashing horizontal bars ” -- -- “.

To enter “TIME MODE”, keep the SET button pressed

•
until gures ash on the LED panel.

(Hours are to the left and minutes to the right.)•
Press the SET button to adjust to local time. AM/PM •
should also be set here.
Store each setting by pressing the AUTO button (NEA •

1402) - AUTO/STORE button (NDA 1402) or use the
automatic store function (wait 5 sec.).

HOURS

HOURS

MINUTES

NDA1402

MINUTES

note: It is important to check the clock setting every

month and to reset when entering different time zones.
This is to allow proper defrosting daily at 1:00 am.

Press the SET button to set the thermostat. Thermo-•
stat range is 1 to 5, where 5 represent’s the coldest
compartment temperature.

Press the STORE button to store or use the automatic

•

store function (wait 5 sec.).

manual defroSt

NDE1402

NDA1402

The refrigerator can be set to defrost at any time. Usu­ally a defrost cycle takes about 1 hour but will depend on
the amount of frost and could therefore vary from time to
time.

•

Switch off the refrigerator with the ON/OFF button.
Press and hold the AUTO button (NEA 1402) - AUTO/ •

STORE button (NDA 1402). Then, press the ON/OFF
button. “dE Fr” is displayed.

11

13

The drip tray catches small
spills. The tray is removable
and dishwasher safe.

It is not a drain;
pour water directly into this
area.

DO NOT

Ice dISPenSer (oPtIonal)

For a refrigerator to provide ice through the door, the ice

maker rst dumps the ice it produces into a large bin. To

request ice at the door, select Cube or Crush and then
press the lever. This will activate a switch which turns on
a motor that rotates the auger. When the auger rotates,
it pushes ice out of the bin, through a chute right into the
glass. To stop dispensing, pull the glass away from dis­pensing arm before the glass is full. Allow the ice chute to
clear before removing the glass.

SectIon 2
ac Voltage

ac Voltage reQuIrementS

this is an energized circuit. Shock can occur
if not tested properly. testing is to be done

by a qualied service technician.

The refrigerator is a 120 volt AC, 60 Hz appliance. The
proper operating range is 108 to 132 volts. If the voltage

drops below 108 volts, cooling efciency will decrease as

the voltages decreases. Check the AC volts at the recep­tacle where the refrigerator is attached. If the voltage is
outside of the proper operating range, correct the power
source problem.

120 Volt ac
receptacles

Might have separate
power cords if unit
has an Ice Maker

Water dISPenSer (oPtIonal)

The water dispenser works much like the ice dispenser.
To request water at the door, simply press the lever. This
will activate a switch which turns on an electric water valve

at the back of the refrigerator. Water will ow through a

separate tube right into the glass.

note: The NDA/NDE1402 models use “Non-chilled”

water at the door dispenser.

locK out feature

The ice dispensing system can be locked out to prevent
unwanted use.

lock out•

To lock out, press the “Lock” pad for (3-5) seconds
until the RED light above the Padlock comes on.

unlock•

To unlock, press the “Lock” pad for (3-5) seconds un­til the RED light above the Padlock goes out.

dISPenSer lIgHt

The light can be turned on and off by pressing the “Light”
touch pad. The light will illuminate the dispenser area.
The light will also turn on automatically when ice or water
is dispensed.

automatIc PoWer SuPPly SWItcH off

For safety reasons, when opening the freezer door, the
ice/water dispenser and ice maker system will automati­cally shut off. Closing the freezer door automatically re­sumes operation of ice/water dispensing and ice maker
operation.

The refrigerator is equipped with a three-prong (ground­ing) plug for your protection against shock hazards and
should be plugged directly into a properly grounded three
prong receptacle.
ing prong from this plug! The free length of the cord
is 3 feet. It is recommended that the receptacle is locat­ed to the right side of the refrigerator (viewed from the
rear). The receptacle should be 3” (from the bottom of the

plastic receptacle) above the refrigerator mounting oor.

This allows easy access through the vent door. The cord
should be routed to avoid direct contact with components
that could damage the cord insulation. The refrigerator
will not switch to another mode of operation until all AC
power is lost.

do not cut or remove the ground-

SectIon 3
ac comPonentS

3.1 Heating element

The heating elements are designed to deliver a prede­termined amount of heat to the cooling unit. To check a
heating element, remove the heater leads from the print­ed circuit board and measure for proper resistance across
the two leads with a properly calibrated Ohm meter. This
check is to be done with the heating element at room tem­perature. You should obtain the following readings ± 10%.

1312

model Watts ohms amps

NDA 1402 420 34.3 3.5
NDE 1402 420 34.3 3.5

The NDA/NDE1402 models use two AC heaters wired in
series. The resistance should be 34.3 Ohms +/- 10%.

note: never over or under size the ac heater.

3.2 Interface module

The interface module is used for two reasons:

The tabs on the module are from left to right:

•

(4) Interconnected tabs that serve as intercon­nection points of four neutral wires (white).
(2) Interconnected tabs that serve as intercon-•
nection points of the “auger wire” from the door
and the wire to the auger motor (yellow).
(2) Interconnected tabs that serve as intercon-•
nection points for the “cube wire” from the door
and the wire to the solenoid (red).
(2) Interconnected tabs that supply switched 120

•

volt AC to the door and to the ice maker (black).
(1) Tab for incoming 120 volt AC to the interface •
module (black).

To shut off the 120 volt AC supply to the door dispens-

•

er and ice maker when the freezer door is opened (for
safety Reasons).

To shut off the 120 volt AC supply to the door dispens-•
er and ice maker when the refrigerator is switched
“OFF” by means of the ON/OFF button on the upper
display panel.

The function of this additional module is very simple. It
has a (5 amp) fuse for incoming 120 volt AC line volt­age and a relay that switches the line voltage ON/OFF.
The relay is driven by a circuit that senses the voltage at
the node between the door switch and the interior lamp.
This relay is controlled by the wires in the P1 connec­tor on the interface module. These wires are hooked on
the wires coming from the power module to the lamp and
door switch. The black wire is ground (-), the white wire is
12 volt DC (+) and the yellow wire is going to the connec­tion point between the lamp and door switch. If the door
is opened, the yellow wire should be 12 volt DC (+) and
if the door is closed, the reading should be 0 volts DC. If
the lamp is lit or if 12 volt DC is absent, the relay will drop
out and 120 volt AC will not be supplied to the ice maker
or the door dispenser.

To troubleshoot the module:

Check that the wires are correctly connected to

•

the tabs.
When the door is shut, check that 120 volt AC is •
present on the tabs (J9) and (J10).
When the door is open, check that the voltage on •
these tabs (J9) and (J10) is 0 volts AC.
If 120 volts AC is not present on (J9) and (J10) •
when door is closed, check the fuse.
If the fuse is OK, check that the interior light in the •
freezer is working, (switched on/off when press­ing/releasing the door button).
If the interior light is OK, check if the relay is •
“clicking” when the door is opened/closed (you
will need an assistant to operate the door while

you are touching the relay with a nger to sense

if it is “clicking”.
If the relay is not clicking though the interior light •
is correctly switched ON/OFF, measure the volt­ages on the pins in the P1 connector. The volt­ages should be as described previous, in this
section.
If the voltages in the P1 connector are OK and •
still the relay is not clicking when opening/closing
the door, the module is faulty; the transistor that
drives the relay is probably damaged.

this is an energized circuit. Shock can occur
if not tested properly. testing is to be done

by a qualied service technician.

13

15

3.3 ac Sensing

The incoming 120 volt AC supply is constantly checked
for availability by means of an opto-coupler. There is a
delay of approximately 15 seconds before a change is
recognized to avoid spurious switching. When AC is not
available in AC only refrigerators, the message “no AC” is
shown on the front display panel.

SectIon 4
dc Voltage

4.1 dc Voltage reQuIrementS

Clean Direct Current (DC) power is mandatory for high­tech circuits to operate as designed. A battery will provide
straight line DC power. The converter and alternator pro­duce DC power by a series of diodes that rectify alternat­ing current to DC. The Dometic control system will only
tolerate up to 6 volts AC on the DC line (Also known as
AC ripple). AC ripple can be measured by a digital volt­meter set on the AC scale and measured at the main DC
terminal block connections at the back of the refrigera­tor. 6 volts AC or less is acceptable. If AC volts exceed
6 on the incoming DC line, the power source should be
cleaned. AC voltage in excess of 6 volts will affect the
processor and create erratic operation. When testing for
AC ripple on the DC line put a load on the converter. The
operational range of the unit is a minimum of 8.5 volts
DC to a maximum of 18 volts DC (However 10.5 volts DC
minimum is required to activate the defrost system). The
unit will automatically shut down at 18 volts DC or greater,
and come back on when voltage has decreased to the
proper operating range. The refrigerator requires at least

8.5 volts DC for proper cooling operation. The refrigerator

must be connected to the battery circuit with two wires of
adequate capacity to avoid voltage drop. Proper polar­ity is crucial for refrigerator operation. No other electrical
equipment or lighting should be connected to the refrig­erator circuit. Just because you can read volts, does not
mean you have the amps to operate the control system.
If relays buzz, lights go dim or out during operation, this
could indicate there is a loose connection somewhere. As
a last test, use a battery and run wires directly to the DC
terminal block. If the unit works OK on direct DC voltage
the problem is in the coach, not the refrigerator control
system.

note: The defrosting cycle will not start if the voltage is

below 10.5 volts DC. It is important that the wires to the 12
volt DC terminal block are of proper wire size.

•

Check the wire gauge to ensure that it is in accor­dance with recommended dimensions.

length (ft) min. size (aWg)
< 33 12
33-66 10
> 66 8

4.2 groundS

The operation of the Dometic refrigerator is also depen­dent on good, clean ground connections. Loose or corrod­ed ground terminals create an unknown resistance factor
that can affect the voltage detected by the Power Module.
A loose negative DC wire will create a negative millivolt
signal that the control board will pick up and create erratic
operation. Check the integrity of the grounds from the re­frigerator all the way to the power source/battery. Clean or
tighten any suspicious looking connections.

Main Terminal Block

note: The DC terminal block located on the back of the

refrigerator should be cleaned and tightened at all four
wires.

SectIon 5
dc comPonentS

5.1 door Switches and lamps

Both compartments have interior lights controlled by door
switches. Both lamps are of a halogen type. The lamp
in the freezer compartment is rated at 5 watts, while the
lamp in the fresh food compartment is a 10 watt lamp.
Lamps and switches are directly connected to the power
module. The wires are foamed in and end up in the 10
pin Molex MiniFit P4 connector on the main circuit board.
The lamps are directly controlled from the switches and
the interconnections are on the main board. The proces­sor on the power module cannot control the lamps but
senses if the switches are closed or not, to decide if doors
are open or closed (Used in the diagnostic mode). The
door switches are open when the switch arm is depressed
(interior light should be off). When the door is open the
switch is closed (interior light should be on). Check that
the switch assembly is properly aligned and that it is not
broken. Check the switch assembly for continuity. To do a

continuity check, rst be sure all power is disconnected or

“OFF” to the refrigerator. Second, remove all wires from
the switch assembly, then check the switch. When the
switch is depressed, there should be no continuity. When
the switch is NOT depressed, there should be continuity.
If any of these checks are incorrect, replace the switch.
After the check, be sure the switch assembly is wired
properly per the wiring diagram.

1514

5.2 temperature Sensors

The NDA/NDE 1402 has two sets of thermistors. One
for the freezer and the other for fresh food compartment.
The display range is from - 9° F to 41° F in the freezer
and from - 9° F to 59° F in the fresh food side. For tem­peratures below and above these ranges, the display will
show “Lo” and “hi” respectively.

During normal operation, the temperatures in degrees
Fahrenheit in the compartments are shown on the display,
freezer to the left and fresh food to the right. However,
the shown temperatures are not the ones actually mea­sured. Instead they are calculated as the most probable
temperatures of the food that is stored in the respective
compartment. Therefore these temperatures should not
be compared with temperatures measured with ordinary
thermometers placed inside the compartments. When the
power is switched “OFF” and then “ON” again, the tem­perature lters will forget historical values and the calcu­lation restarts from the beginning. In this case the shown
values will be about 2° F above the real air temperatures
at the sensors.

Each thermistor harness consists of two thermistor sen­sors. One each for “air” and the other for “surface” for the
defrosting process.

Disconnect the thermistor harness from the P2, 4-pin ter­minal (freezer) or P3, 4-pin terminal (fresh food) on the
lower circuit board. Place the sensing tip in a glass of ice
water (more ice than water), approximately 33° F to 35°
F. Wait 8 to 10 minutes. You should get a reading of ap­proximately 5,500 Ohms. Always test from the wire side of
the 4-pin connector with the meter leads as not to create a
connection problem at either the P2 or P3 connector.

note: A disconnected or faulty thermistor will result in an

error code displayed on the front display panel. See sec­tion 11 for trouble shooting error codes.

Fresh food air thermistor:

Remove the P3 connector from the lower control
board. Check the resistance between pins 1 and 2 on
the P3 connector.

Fresh food surface thermistor:

Remove the P3 connector from the lower control
board. Check the resistance between pins 3 and 4 on
the P3 connector.

Freezer air thermistor:

Remove the P2 connector from the lower control
board. Check the resistance between pins 1 and 2 on
the P2 connector.

Freezer surface thermistor:

Remove the P2 connector from the lower control
board. Check the resistance between pins 3 and 4 on
the P2 connector.

note: See page 49 for thermistor values at varying tem-

peratures.

5.3 low ambient control

The automatic Low Ambient Control ensures trouble free
operation in low ambient temperatures (e.g. Below 50° F).
In colder weather, the temperature inside the fresh food
compartment tends to hold the temperature inside for a
very much longer period of time, with very long periods
in between ON/OFF cycling of the heat source; this is OK
for any food product inside the fresh food compartment,
but is not OK for the freezer compartment. The NDA/
NDE1402 have active thermostatic control of both com­partments (however, you can only set the temperature
level for the fresh food thermostat). If the temperature in
the freezer is not low enough, the cooling is switched on.
If the fresh food compartment then becomes too cold, the
defrosting element will be switched on to keep it at the
correct temperature.

Air sensor

4-pin connector

Surface
sensor

5.4 frame Heater

The frame heater is located behind the metal frame be­tween the doors. The heater helps to reduce sweating on
the metal frame during periods of high humidity. The heat­er is on all the time except during the defrosting phases
to reduce maximum current draw from the DC supply. To
test the heater, remove the white wire from terminal (J4)
and measure the resistance between the wire removed
and chassis ground. You should have a resistance read­ing of 24 Ohms +/- 10%.

note: Some units may have a Light blue wire on J4.

15