CSR-20 & CSR-40, September 1999
µ
P-D Controller
Diagnosis and Repair
4-45
• Ambient sensor must be placed on the bottom plate of the
right forklift pocket.
• Compressor discharge temperature sensor must be placed in
the sensor pocket on the top of the compressor. The sensor
tip is inserted special thermal conducting grease, P/N 203-
454, in the bottom of the pocket. An O-ring seal and RTV
compound seals the top of the pocket.
Semiconductor Type Sensors
Electronic semiconductor type temperature sensors are used
for:
• Supply Air
• Return Air
• Evaporator Coil
• Condenser Coil
• Ambient Air
Semiconductor sensors can not be checked with an ohm-
meter. If an alarm code indicates a sensor failure, check the
sensor by substitution. The supply air, return air and evapora-
tor coil sensors are graded sensors. Graded sensors can also be
ice bath calibrated. The
µ
P-D controller will not operate cor-
rectly if the return air, supply air and evaporator coil sensors
are not ice bath calibrated or the correct sensor grades are not
in the controller.
The condenser coil and ambient air sensors are non-grad-
ed sensors. Non-graded sensor do not require ice bath calibra-
tion.
Thermistor Type Sensors
Thermistor type temperature sensors are used for:
• Compressor Discharge Gas Temperature Sensor
If an alarm code indicates a failed sensor, check the sensor
by substitution.
Diagnosis and Repair
If the unit appears to be operating incorrectly, view any alarm
codes that may be stored in the controller display memory.
Diagnose and correct the problem associated with each alarm
code (see “Alarm Codes, Descriptions and Corrective Actions”
in this chapter).
If you have viewed and corrected these problems and the
unit still appears to be operating incorrectly, eliminate any
possibility that the problem is caused by failure of components
other than the controller.
External Cause Checks
•
Poor contact between male and female connector plugs
(loose connection).
•
Defective wire harness (broken wires, loose connections).
•
External electrical causes such as faulty (open or stuck)
contactors.
•
Malfunction of refrigeration system components.
NOTE: For complete diagnosis and corrective action
information about the controller and unit compo-
nents, see the Diagnosis Manual for THERMO-
GUARD
µµ
P-D Microprocessor Controller, TK 41230.
Evaporator Coil Sensor Location — Units with Two
Evaporator Fans
A.
Coil Support Bracket
B.
Unit Front
C.
Insert Sensor between Tube Rows 2 and 3
