Thetford NR740 User Manual
Service Manual
DCXXXX, DEXXXX Model
Compressor Refrigerators
MODELS
DC0040(K), DC0051(K)
DE0040, DE0051
DE0240T, DE0251T
DC0740(X), DE0740(X)
DC0751(X), DE0751(X)
Please note that the "X" at the end of certain model
numbers indicates the equipment color; where "X" can
be "B" (black), "S" (stainless steel, or "W" (wrapped
door - stainless steel).
© 2007 NORCOLD, INC. All rights reserved.
Part No. 631842A (08-08-07)
Table of Contents
!
Troubleshooting - Procedure A
Compressor Doesn't Run with Thermostat "On" .............3
Troubleshooting - Procedure B
Compressor Resistance .................................................. 4
Measuring the Compressor Resistance ..........................4
Troubleshooting - Procedure C
Power Supply Output Voltage .........................................5
Troubleshooting- Procedure D
Measuring Compressor Amp Draw .................................6
Troubleshooting - Procedure E
Verifying Thermistor Operation .......................................7
Troubleshooting - Procedure F
Insufcient Cooling .......................................................... 8
Troubleshooting - Procedures G
Refrigerator is Too Cold ..................................................8
Troubleshooting - Procedure H
Auto Shut-Off Device.......................................................8
Operating the Shut-Off Device ....................................8
Troubleshooting - Procedure I
Proper Ventilation ............................................................9
Wiring Schematic ............................................................9
Troubleshooting - Quick Reference
Quick Reference Troubleshooting Steps.......................10
WARNING! Perform all tests using a fully
charged 12V DC battery. Using other equipment that supplies DC voltage may cause
permanent refrigerator component failure.
2
DC0040(K), DC0051(K), DE0040, DE0051, DE0240T, DE0251T,
DC0740(X), DE0740(X), DC0751(X), DE0751(X) Models
Refrigerator Service Manual
Troubleshooting - Procedure A
Thermostat “ON” Compressor Does Not Run
Measure Terminal
Voltage Of Temperature
Control Between TP1 &
TP2. (See Figure 1)
DC 0V
DC 5V
DC 2V
Short Circuit
Normal
DC Power
Supply Failure
Change DC
Power Supply
Change DC
Power Supply
See
Procedure B
Measure Terminal
Voltage of Temperature
Control Between TP2 &
TP3. (See Figure 1)
Is Temperature
Control LED on?
YES
NO
Correct
Voltage
OK
Check Supply
Voltage
(10.5 – 32V DC)
(85 – 132V AC)
CORRECT
INCORRECT
Compressor
Runs
YES
NO
Replace
10A Fuse
(See Figure 2)
Reverse Polarity
& Check Operation
(Red + / Black -)
OK
Replace
10A Fuse
(See Figure 2)
OK
Check DC
Polarity
INCORRECT
OK
Compressor
Runs
YES
NO
Check Both
DC Fuses
BLOWN
OK
Compressor
Runs
YES
NO
DC 0V
DC 12
to 32V
DC Power
Supply Failure
Normal
Change DC
Power Supply
See
Procedure B
Note: Measurements taken with 12.8V DC or 120V AC power supply.
Check AC
Power Supply
(37 – 45V DC)
(See Figure 5)
Change AC
Power Supply
Short Circuit
Change DC
Power Supply
GOOD
BAD
AC
OPERATION
DC
OPERATION
Power
Source
DC
AC
Check AC
Power Supply
(37 – 45V DC)
(See Figure 5)
DC Power
Supply Failure
Change DC
Power Supply
Change AC
Power Supply
GOOD
BAD
DC
OPERATION
AC
OPERATION
ART01945
ART01944
Brown
Red
Black
ART01946
Compressor Doesn't Run with Thermostat "On"
Refrigerator Service Manual
Figure 1. Temperature Control
DC0040(K), DC0051(K), DE0040, DE0051, DE0240T, DE0251T,
NOTE: If 10 Amp fuse is blown, check the vehicle's wiring.
Figure 2. Fuse Locations
DC0740(X), DE0740(X), DC0751(X), DE0751(X) Models
3
Troubleshooting - Procedure B
Compressor Resistance
Measure
Compressor
Resistance.
See Figure 3.
0
1.4 – 3.5
Normal
Internal
Compressor
Failure
See
Procedure C
Change
Cooling Unit
Note: Perform procedure at room temperature.
ART01947
ART01958
B
A
Compressor Resistance
Measuring the Compressor Resistance
Turn the temperature control to the "Off" position.1.
Remove the black wire to the compressor.2.
Measure the resistance of the compressor between point 3.
A and point B. Refer to Figure 3.
4
DC0040(K), DC0051(K), DE0040, DE0051, DE0240T, DE0251T,
DC0740(X), DE0740(X), DC0751(X), DE0751(X) Models
Figure 3. Measuring Compressor Resistance
Refrigerator Service Manual
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