50
EXV Troubleshooting Procedure —
Follow steps
below to diagnose and correct EXV/Economizer problems.
Check EXV motor operation first. Switch the Enable/Off/
Remote (EOR) Contact switch to the Off position. Press
on the Navigator until ‘Select a menu item’ appears on the dis-
play. Use the arrow keys to select the Service Test mode. Press
. The display will be:
> TEST
OFF
OUTS
COMP
Press
(password entry may be required) and use
to change ‘OFF’ to ‘ON’. Switch the EOR switch to
Enable. The Service Test mode is now enabled. Move the
pointer down to the OUTS sub-mode and press
. Move the
pointer to item EXV.A or EXV.B as needed. Press
and
the valve position will flash. Use
to select 100% valve
position (hold
for quick movement) and press
.
You should be able to feel the actuator moving by placing
your hand on the EXV. A sight glass is located on the valve
body to verify that the sleeve is moving to expose/cover slots in
the orifice. A hard knocking should be felt from the actuator
when it reaches the top of its stroke (can be heard if surround-
ings are relatively quiet). Press
again twice if necessary to
confirm this. To close the valve, press
, select 0% with
and press
. The actuator should knock when it reaches
the bottom of its stroke. If it is believed that the valve is not
working properly, continue with the checkout procedure
below:
Check the EXV output signals at appropriate terminals on
the EXV module (see Fig. 21). Connect positive test lead to red
wire (EXV-J6 terminal 3 for Circuit A, EXV-J7 terminal 3 for
Circuit B). Set meter to approximately 20 vdc. Using the
Service Test procedure above, move the valve output under test
to 100%. DO NOT short meter leads together or pin 3 to any
other pin as board damage will occur. During the next several
seconds, carefully connect the negative test lead to pins 1,2,4
and 5 in succession (plug J6 for Circuit A, plug J7 for Circuit
B). Digital voltmeters will average this signal and display ap-
proximately 6 vdc. If it remains constant at a voltage other than
6 VDC or shows 0 volts, remove the connector to the valve and
recheck.
The EXV motor moves at 300 steps per second. Command-
ing the valve to either 0% or 100% will add 7500 steps to the
move. For example, if the EXV is fully closed, selecting 100%
would allow 75 seconds for the dc voltage to be checked
(15,000/300 + 7500/300).
Press
and select 0% to close the valve. Check the 4 po-
sition DIP switch on the board (all switches should be set to
On). If a problem still exists, replace the EXV module. If the
reading is correct, the expansion valve and EXV wiring should
be checked. Check the EXV terminal strip and interconnecting
wiring.
1. Check color coding and wire connections. Make sure
they are connected to the correct terminals at the EXV
driver and EXV plug and that the cables are not crossed.
2. Check for continuity and tight connection at all pin
terminals.
Check the resistance of the EXV motor windings. Remove
the EXV module plug (J6 for Circuit A, J7 for Circuit B) and
check the resistance of the two windings between pins 1 and 2
for one winding and pins 4 and 5 for the other winding (see
Fig. 21). The resistance should be 75 ohms ± 7.5 ohms.
INSPECTING/OPENING ELECTRONIC EXPANSION
VALVES
To check the physical operation of an EXV, the following
steps must be performed.
1. Close the liquid line service valve of the circuit to be
checked. Put the Enable/Off/Remote Contact switch in
the Off position. Using the Navigator, enter the Service
Test mode and change the sub-mode TEST from ‘OFF’
to ‘ON’. Switch the EOR switch to the Enable position.
Under the COMP sub-mode, enable the desired compres-
sor (CC.xx) for the circuit. Let compressor run until gage
on suction pressure port reads 10 psig. Press
,
and
to turn the compressor off. The compressor will
complete its pumpout routine and turn off. Immediately
after the compressor shuts off, close the discharge valve.
2. Remove any remaining refrigerant from the system low
side using proper reclaiming techniques. Drain oil from
cooler using Schrader port in cooler inlet line. Turn off
the line voltage power supply to the compressors and
control circuit power.
3. The expansion valve motor is hermetically sealed inside
the top portion of the valve. Carefully unscrew the large
retaining nut securing the motor portion to the body of the
valve making sure the EXV plug is still connected. The
EXV lead screw and sleeve will come off with the motor
portion of the device.
4. Enter the appropriate EXV test step under the OUTS sub-
mode in the Service Test mode. Locate the desired item
‘EXV.A’ or ‘EXV.B’. Press
to make the valve posi-
tion of 0% flash. Press and hold
until 100% is
displayed and press
. Observe the operation of the
lead screw and sleeve. The motor should be turning the
lead screw and sleeve counterclockwise, raising the
sleeve closer to the motor. Lead screw movement should
be smooth and uniform from fully closed to fully open
position. Press
, use
to select 0% and press
again to check open to closed operation. If the valve is
properly connected to the processor and receiving correct
signals, yet does not operate as described above, the
sealed motor portion of the valve should be replaced.
ESCAPE
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
IMPORTANT: Obtain replacement O-ring before open-
ing EXV. Do not reuse O-rings.
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
Fig. 21 — EXV Cable Connections to EXV Module
