Thermo King T-500R Maintenance Manual page 219

WARNING: If the ETV is stuck in the closed position, much of the refrigerant charge may be trapped in the
evaporator. If you hear refrigerant begin to flow through the valve when the stepper motor and piston assembly are
loosened, unscrew the Old Style ETV stepper motor and piston assembly no more than four turns, or unscrew the four
screws on New Style ETV stepper motor no more than four turns each, and check the suction (low side) pressure on
the gauge manifold. If the suction pressure has increased from the pressure to which it was equalized after the low
side pump down, refrigerant is trapped and must be recovered. Screw the stepper motor and piston assembly back into
the valve body. Attach a refrigerant recovery device to the service port on the receiver tank outlet valve. Midseat the
receiver tank outlet valve, and recover the refrigerant charge. The stepper motor and piston assembly may then be
removed.
4. Old Style ETV - Unscrew the large nut that attaches the stepper motor and piston assembly to the valve body. The torque on
the nut is approximately 118 fT-lb (160 N•m). Hold the valve body with backup wrench to prevent damage to the refrigeration
tubing.
New Style ETV - Remove the four screws that attach the stepper motor to the valve body.
CAUTION: Old Style ETV - Unscrew the large nut. Do not unscrew the small hex on the stepper motor.
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1. Unscrew Large Nut
2. Backup Wrench
Removing Old Style Stepper Motor
5. If the complete ETV assembly is being replaced, remove the ETV mounting hardware and unsolder and remove the valve
body. It may be necessary to unsolder other tubes near the valve body to obtain enough clearance to remove the valve body.
Note the position of the valve body so the new one will be placed in the same position.
Installation of Service Kit
Do not connect the ETV harness or ETV to main wire harness and turn the unit on before the stepper motor and piston
assembly is installed in the valve body. The controller is programmed to close the ETV when the unit is turned on. If the unit
is turned on with the ETV harness connected to main wire harness, the controller will attempt to close the ETV. This will cause
the piston to be turned (screwed) off the threaded shaft of the stepper motor because the valve body is not present to stop it.
Further disassembly is required to reassemble the piston and stepper motor. See "Reassembly of Piston and Stepper Motor on
Old Style ETV".
1. The new stepper motor and piston assembly is supplied with the piston in the open position. In the open position the bottom
edge of the piston is 0.3 to 0.7 in. (8 to 18 mm) from the bottom edge of the brass nut/piston housing. The piston retracts to
open and extends to close.
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Refrigeration Maintenance
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ARA2500
1. Remove Four Screws
Removing New Style Stepper Motor
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