Electronic Expansion Valve
RTHC-SVD01B-EN 47
Section 8 Electronic Expansion Valve
8-1. General
The Electronic Expansion Valve is a flow device which meters refriger-
ant into the evaporator as necessary. The valve uses a stepper motor
consisting of two windings to modulate the.
The Stepper module monitors the liquid level under normal operating
conditions and controls the EXV with the level of refrigerant in the
evaporator. If the liquid level rises above the optimum value of 0.0” as
displayed on the UCM the EXV will begin to close. If the liquid level
falls below the optimum value of 0.0” as displayed on the UCM, the
EXV will begin to open.
A malfunctioning EXV can exhibit several different diagnostics. A diag-
nostic will appear if the EXV is failing electrically or if the stepper mod-
ule is defective. Use the following procedure to determine the cause of
the diagnostic.
8-2. Stepper Module Checkout Procedure
The Stepper module must be powered for the operation of the elec-
tronic expansion valve. If any of the voltages listed in 8-1are out of
range, either the 1U3 is receiving no or improper power, or the 1U3
Stepper module is malfunctioning.
If the voltages do not fall within the acceptable range, the Stepper
module needs to be replaced.
Table 8-1: Stepper Module Voltage Limits for EXV
Connector Voltage (VAC) Voltage (VDC)
J2-1 to J2-2 20.4 to 33.12 0
J2-1 to case 10 to 17 13.12 to 21.81
TP1 (35V) to ground 100 mVAC to 72 mVAC 26 to 48
TP2 (5V) to ground 0 4.8 to 5.2
TP3 (14V) to ground 0 11.45 to 15.75
TP4 (24V) to ground 0 23.2 to 25.1
To Next Page
Loading...
