Thermo King SR-2 SmartReefer2, Diagnostic Manual

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Section 2 – SR-2 Hardware Description
Hot Gas Solenoid (HG)
The normally closed hot gas bypass solenoid is
opened during modulated cool when the
temperature is very close to setpoint. This diverts
hot gas from the compressor discharge line, through
the open hot gas solenoid to the evaporator
distributor, to further reduce cooling capacity. The
valve also opens if the suction pressure is too low.
This valve is supplied on ETV equipped units only.
The hot gas solenoid is energized and LED 10 is lit
when the microprocessor energizes the Hot Gas
Solenoid Smart FET. This supplies power via the
HG wire to the hot gas solenoid. The circuit is
protected by the Smart FET.
Damper Solenoid (DS)
A damper solenoid is used to open and close the
defrost damper doors. Damper solenoids are used
on most US domestic units. The interface board for
units with damper solenoids is different than the one
used with defrost damper motors. See the
information in Section 7 - Hardware Features and
Interchange for Service Parts numbers.
The damper solenoid is energized and LED 4 is lit
when the microprocessor energizes the K4 Damper
Relay. The K4 Damper Relay normally open
contacts supply power via the 29 wire to the damper
solenoid. The circuit is protected by the 15 amp
fuse F6.
Damper Motor
European SL units use defrost damper gear motors
to open and close the defrost damper door. The
interface board for units with damper solenoids is
different than the one used with defrost damper
motors. See the information in Section 7 - Hardware
Features and Interchange for Service Parts
numbers.
A damper motor heater is utilized with damper motor
applications. The damper solenoid output is used to
control the damper motor heater. The heater is part
of the damper motor assembly.
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31 January 2005