Thetford NR740 - Manual (Page 3)

Refrigerator Service Manual 3 DC0040(K), DC0051(K), DE0040, DE0051, DE0240T, DE0251T,
DC0740(X), DE0740(X), DC0751(X), DE0751(X) Models
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
AR
T0
19
45
AR
T01944
Brown
Red
Black
Figure 1. Temperature Control
AR
T01946
Figure 2. Fuse Locations
NOTE: If 10 Amp fuse is blown, check the vehicle's wiring.
Compressor Doesn't Run with Thermostat "On"