Thermo King 098203, Maintenance Manual

Page: 167 / 264

Electrical Maintenance
165
Installing Temperature Sensors
All sensors should be properly installed as follows:
• Supply air sensors must be inserted to the bottom of the sensor tube and completely sealed by the
grommet connection.
• Return air sensor installs in a grommet between the evaporator fans.
• Evaporator coil (defrost) sensor must be placed in the middle of the coil and 75 mm deep between the
fins.
• Condenser sensor must be placed on the upper left side of the condenser coil and 70 mm deep
between the fins.
• Ambient sensor must be placed on the bottom plate of the right forklift pocket.
• Compressor discharge temperature sensor is attached to compressor head by adhesive. See
“Compressor Discharge Temperature Sensor Replacement” in the chapter for Refrigeration System
Diagnosis and Service.
Testing the Sensors
The controller constantly monitors the left hand and right hand supply sensors, return sensor and defrost
(evaporator coil) sensor to determine when to initiate a demand defrost. If a demand defrost is requested
and defrost has occurred within the last 90 minutes, the controller initiates a probe test to check for a
defective sensor.
During a Probe test, the VGA display shows [PROBE TEST PLEASE WAIT]. The controller operates the
unit on high speed evaporator fans only for 5 minutes. All sensor temperatures are then compared:
• Sensors with large temperature differences are discarded from the control algorithm. The controller
then activates the appropriate Alarm codes to identify the defective sensor(s).
Sensor errors recorded during a probe test are cleared when the next Defrost is initiated or Unit On/Off
switch is turned Off.
NOTE: A manual probe test can be performed by a technician by selecting “SENSOR CHECK” from
the Manual Test Function menu.