Thermo King 098203, Maintenance Manual

Page: 229 / 264

Diagnosis: Troubleshooting, Warnings and Alarm Codes
227
04 Evaporator Coil Sensor Open Circuit
• When the sensor circuit resistance is higher than
1300
Ω
.
• Indicates:
• Open circuit.
• Defective or wrong sensor.
• Defective wiring.
• Defective controller.
• Check for damaged sensor wires.
• Check sensor connections at controller.
• The sensor is a pt1000 – 2 wire sensor,
connected to the MP-4000 at connector J3 pin
5 and 6. CM-4000 upper left connector J3, 17
pin wide, pin number 1 is the right pin, seen at
the backside of the controller.
• The 2 sensor wires can be switched without
affecting the measurement.
• Disconnect the sensor, use an Ohm (
Ω
)
measuring device, measure the electrical
resistance between the two sensor wires.
The sensor can’t be examined without
disconnecting it.
The electrical resistance towards chassis must
be above meg ohm (M
Ω
) range.
• The sensor is a pt1000 – positive temperature
coefficient, which means that the electrical
resistance of the sensor increases with
temperature.
The sensor is defined to be 1000
Ω
@ 0°C.
Normal condition measuring with
disconnected sensor is 960
Ω
@-10°C,
1000
Ω
@0°C,1039
Ω
@+10°C, 1058
Ω
@+15°C,
1078
Ω
@+20°C.
The valid measuring limit for this pt1000
sensor is -100°C(602
Ω
) +75°C(approx
1300
Ω
).
Alarm Codes, Descriptions and Corrective Actions (Continued)
Code Description Corrective Action