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Electronic Expansion Valves
CHECKOUT PRCKEDCRE
~
1-<11low
steps
below
to
diagnose and correct EXV problems, For an explanarjon
of EXV operation, see
paye
2
1.
Step 1
-
Check EXV Driver Outputs
~
Chcuk
l_XV
output signals at appropriate terminals on
the
E.YV
driver
module (Fig. 8) as
folIows:
Connect positive test
lcad
to terminal 1 on EXV driver.
Set meter for approximately 20
vdc.
Enter outputs sub-
function of test function by pressing
m
‘4
, then
advance to EXVA Open Quick Test by pressing
h 5
times. Press
iRmIl
El
ENm
. The driver should drive the EXV fully
open. During the next several seconds connect the nega-
tive test lead to pins 2. 3, 4 and 5 in succession. Voltage
should rise and fall at each pin. If it remains constant at a
voltage or at zero volts, remove the connector to the valve
and recheck. Press to reach the EXV A
Close
Quick
Test. If a problem still exists, replace the EXV
driv’er.
If
the voltage reading is correct, the expansion valve should
be checked. Next, text EXVB. Connect the positive test
lead to pin 7 and the negative to pin
8,9,
IO,
1
l
in succes-
sion during the EXVB Quick Test.
Step 2
-
Check EXV Wiring
~
Check wiring to elec-
tronic expansion valves from terminal strip on EXV
driver (Fig.
8).
2. Check for continuity and tight connection at all pin
terminals.
3.
Check plug connections at driver and at EXVs. He sure
EXV connections are not crossed.
Step 3
~
Check Resistance of EXV Motor Windings
~
Remove
rnBug
at
137
terminal strip and check resistance
1.
Check color coding and wire connections. Make sure
they are connected to correct terminals at driver and
between
c’ommon
lead (red wire, terminal
Uj
and remain-
EXV plug
connections.
ing leads A,
B,
C. and E (see Fig. 8). Resistance should
be 25 ohms
-t-i’
-2 ohms.
12.
EXV A
Fig.
8
-
EXV Cable Connections to
EXV Driver Module
19