G04A - Electronic Throttling Valve (Etv) Mechanical Operation Test - Thermo King SLX Series Diagnostic Manual

G04A - Electronic Throttling Valve (ETV) Mechanical Operation Test

P P u u r r p p o o s s e e : :
To confirm proper mechanical operation of the Electronic Throttling Valve.
N N o o t t e e : : If the ETV must be changed, refer to the Maintenance Manual for the specific unit.
M M a a t t e e r r i i a a l l s s R R e e q q u u i i r r e e d d : :
• Stepper Valve Tester
O O p p e e r r a a t t i i o o n n : :
This procedure should be used to check mechanical operation of the Electronic Throttling Valve (ETV) whenever an ETV
is suspected faulty. Alarm Code 89 indicates that refrigeration system pressures did not respond as expected when the
ETV was opened and closed, or that an electrical fault with the ETV system was detected. Other alarm codes may be
generated if the ETV fails to regulate suction pressure, such as Alarm Codes 10 and 18. These alarms may be caused by
a malfunction in the ETV or associated circuit.
The ETV contains a Stepper Motor that moves a piston located in the valve body. The piston position in the valve body
determines the amount of refrigerant flow through the valve. Refrigerant flow through the valve is decreased as the
piston is extended into the valve body. Suction pressure will drop as the amount of flow through the valve decreases.
As the piston retracts, more refrigerant is able to flow through the valve and suction pressure increases.
The position of the ETV can be read in the Gauges Menu. A position of 0 indicates the piston is fully extended in the
valve body and that the valve is fully closed. A position of 800 indicates the piston is fully retracted and that the valve is
fully open.
E E l l e e c c t t r r o o n n i i c c T T h h r r o o t t t t l l i i n n g g V V a a l l v v e e T T y y p p e e s s a a n n d d W W i i r r e e C C o o l l o o r r C C o o d d e e s s : :
The round style ETV does not have a removable connector on the valve. There is a sheathed cable consisting of colored
wires that run from the valve to the Deutsch connector on the cable. The Stepper Motor Tester is connected to the ETV
using this Deutsch connector. A pigtail must be constructed in order to connect the tester to the ETV. The ETV may
operate backwards if the connections are reversed. The square tyle ETV has a change in design of the valve body and
stepper motor. It also has an integrated four-pin Deutsch connector located at the end of the stepper motor (no
harness). The square design allows for ease of service and a low torque setting, providing low strain to piping during
service and repair work.
When using the Stepper Motor Tester, the ETV position displayed on the HMI does not indicate actual valve position;
the valve is being controlled manually by the tester. The unit harness from the Base Controller must be disconnected
from the valve at the Deutsch plug in order to connect the ETV tester. The Base Controller will attempt to control the
valve position but will be unable to since the valve is disconnected. The HMI will display requested ETV position,
however, the valve will not respond to requests from the Base Controller and the displayed position will likely not be
the actual position of the valve. Alarm Code 89 will likely not be generated in this case.
I I m m p p o o r r t t a a n n t t : : DO NOT open the valve too far, this may cause a possible Alarm Code 10 in high ambient or stall the engine
if in low speed.
The harness wire number, wire color on ETV, and binding post color on the tester are shown in the table
318).
Round Style ETV
TK 56487-2-OD-EN
Square Style ETV
S S e e c c t t i i o o n n 6 6 - - S S e e r r v v i i c c e e P P r r o o c c e e d d u u r r e e s s
(Table 70, p.
317