Section 5 – SR-2 Diagnostics
ALARM CODE DIAGNOSTICS
00 NO ALARMS EXIST
Page 1 of 1
02 CHECK EVAPORATOR COIL SENSOR
Page 1 of 2
Alarm Type
Check Alarm
(Shutdown Alarm during a Pretrip Test).
Associated Alarm
Codes
Alarm Code 13
Component Description and Location
This sensor is an un-graded sensor and does not require calibration. The sensor is located on the evaporator coil
header plate.
Circuit Description
The evaporator coil temperature sensor circuit is a two wire circuit. The CTP-01 (+) wire connects the
microprocessor 35 pin sensor connector J3 pin 25 to the blue sensor wire. The CTN-01 (-) wire connects the
microprocessor 35 pin sensor connector J3 pin 14 to the brown sensor wire. The sensor wires are routed in the
Sensor Harness. The sensor is hard-wired to the sensor harness.
Considerations
1. Sensors should be positioned to minimize the potential for moisture entry where the wires enter the sensor
shell. Mount sensors with the barrel up and the wires down wherever possible.
How Alarm is Set
1. The sensor is over or under range for a specified time interval. The sensor reading may return to normal.
Only Alarm Code 02 Check Evaporator Coil Sensor is set.
2. The sensor reading is erratic over time but did not go over or under range. Both Alarm Code 02 Check
Evaporator Coil Sensor and Alarm Code 13 Sensor Check are set. This indicates the sensor was
inaccurate but was not over or under range.
3. The differential between the coil and other sensors is too large and the condition is not related to
evaporator coil icing.
How Alarm is Cleared
This alarm is cleared manually. When the alarm is cleared the return air sensors, discharge air sensors and
evaporator coil sensor must all read within a specified number of degrees of each other. If they do not, it is
assumed that the sensor reading is not accurate and the alarm code is not cleared. If the sensor is over or under
range when the alarm clear is attempted, the alarm will not be cleared.
5-9
02 February 2005
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