52 Troubleshooting
SERVO BUTTERFLY VALVES
The servo valve does the actual controlling or ad-
justing of the flow mate. If the servo valve is not
functioning properly the gallons-per-acre readout
will fluctuate by more than +/-10% or the RATE per
acre will remain extremely low or high. If the servo
valve is not functioning correctly, the 8160 can still
be used as a monitor by putting the RATE 1, RATE
2 switch in the MANUAL (center) position.
Make sure your cables are connected properly.
Check setup question “Inline system?” If the ques-
tion was answered yes, then the “ ” key should
OPEN the valve to increase flow to the boom. IF
the question was answered no, then the valve is
mounted in a return line to the tank or the input of
the pump. In this case, the “ ” key should CLOSE
the valve to increase flow to the boom.
Check the valve response number. If the 8160
does not adjust the flow fast enough for speed
changes, increase this number.
If the 8160 GPA readout fluctuates excessively,
decrease this number.
The 8160 console applies a discontinuous posi-
tive voltage level (short pulses of voltage) to the
gear motor. This causes the servo gear motor to
run “jerky.” With a voltmeter, check between cable
connector pins 2 and 3 on the servo cable. You
should get a readout of 1 to 8 volts when the RATE
1/MAN/RATE 2 switch is in the center (manual) po-
sition and the “ ” or “ ” key is depressed. If there
is no voltage during this test, refer to Cable and
Connector troubleshooting or the console could be
defective. If there is voltage, and the motor does
not turn the butterfly the motor may be burned out.
There may be some-thing binding the butterfly or
the set screws on the switch cam may be loose.
2- WIRE SERVO
The 2-wire servo valve only uses 2 and 3 on the
servo cable. Unlike the 3-wire servo valve pin 1 is
not used.
The 8160 discontinuous positive Voltage level to
either pin 2 or 3 to operate the valve. The 8160
can vary the discontinuity times to vary the valve
speed.
There are two switches that will keep the valve
in one quadrant (1/4 turn of the valve).
There is no feedback (pin 1) to the 8160 to let it
know if it is full open or full closed.
If the 8160 tries to increase the flow after the
2-wire servo has reached the full open position,
the motor will stop, the 8160’s %Error will in-
crease, and the Rate reading will decrease.
NOTE:
The following assumes the 8160 is setup
for an “Inline System”.
Normal operation is in the quadrant where the
top switch is normally pressed and the bottom
switch is normally released.
To see if the gear motor and position switches
are functioning properly put the RATE 1/ MAN/
RATE 2 switch in the center (manual) position
and press and hold the “ ” key. This should
drive the valve fully open. When the cam turns
far enough to deactivate the top position switch,
the servo gear motor should stop and the valve
should be full open. If the valve does not stop
when the switch is deactivated, the valve is in
need of repair and should be repaired or re-
placed.
Now press and hold the “ ” key. This should
drive the valve fully closed. When the cam turns
far enough to activate the bottom position switch,
the servo gear motor should stop and the valve
should be full closed. If the valve does not stop
when the bottom switch is activated, the valve
is in need of repair and should be repaired or
replaced.
NOTE:
If the valve has been dissembled or the
motor has had power applied directly to its ter-
minals, the valve may not be in the proper quad-
rant. Press and hold the “ ” key until it stops
rotating (less then 1 revolution). It should now
operate as explained in the previous paragraph.
Summary of Contents for 8160
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