Thermo King SR-2 SmartReefer2, Diagnostic Manual

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Section 5 – SR-2 Diagnostics
30 DEFROST DAMPER STUCK
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Alarm Type Check Alarm
Associated Alarm
Codes Alarm Code 137 Check Damper Motor Heater Output
Component Description and Location
The defrost damper door is located in the discharge air stream at the top of the unit. It is closed during defrost to
prevent warm air from being circulated over the load. The Damper Gear Motor is mounted just outside the
discharge plenum and is connected to the damper door by means of mechanical linkage.
Circuit Description
The damper motor circuit is a two wire circuit. The GM- (black) wire is connected to one side of the damper gear
motor and the GM+ (red) wire is connected to the other side of the gear motor. The motor wires are routed in the
Main Harness. The Damper Heater wires 8F-01 and CH-19 are also routed in the Main Harness.
How Alarm is Set
1. This alarm is set as a Check alarm if the damper gear motor draws excessive current for a specified time.
This indicates that the damper is frozen or stalled.
How Alarm is Cleared
This alarm is cleared manually.
Considerations
1. The damper gear motor requires an interface board equipped with damper motor provisions. The Service
Part Number for the interface board with damper gear motor provisions is 41-5363.
2. Power for the damper heater requires the run relay to be energized.
Diagnostic Procedure
1. Check the operation of the damper door gear motor circuit, using Interface Board Test Mode. Be sure
LED31 Damper Door Open and LED32 Damper Door Close light as appropriate.
2. The initial (breakaway) current draw occurs over a very short period of time and cannot be accurately
measured. Once the motor is running the current draw should not exceed 0.8 amps.
3. Check for ice buildup between the damper blade and damper housing. Breaking the ice may cause
excessive current draw.
4. Check the door and linkage for binding, ice or other restrictions to proper door operation.
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02 February 2005