ARAG Electriccontrol unit for crop-spraing application 871 - Manual (Page 28)

28
FAULT CAUSE REMEDY
Adjustment inaccurate: minor
movements of switch on propor-
tional valve control device lead
to significant change in pressure
Proportional valve not correctly sized
for system
• Change proportional valve.
Insufficient liquid delivery to control
unit
• Check pump rate.
• Increase pump RPM.
• Check for open branches or drain utlets
upstream of control unit.
Large amount of pressure
fluctuation when one or two
sections are closed
Metered by-passes not adjusted • Adjust metered by-passes.
Pressure gauge reading higher
than actual pressure
Pressure gauge malfunctioning • Change pressure gauge.
Squashed gasket inside pressu-
re gauge is partially obstructing
passage
• Slightly loosen pressure gauge.
Passages across valve and nozzle
undersized, leading to significant
pressure drop
• Choose section valve tubes and hose tails
of correct size.
Pressure sensor reading higher
than actual pressure
Sensor malfunctioning
• Change data settings in computer; if
problem persists, change sensor.
Passages across valve and nozzle
undersized, leading to significant
pressure drop
• Choose section valve tubes and hose tails
of correct size.
One or more sections not clo-
sing correctly
Section valve motor not working
• Check electric connection.
• Have gearmotor inspected at the nearest
Service Centre.
Section valve plug gasket worn out • Change worn gaskets.
Chemical residue on gasket and seat
of section valve hose tail
• Clean parts with suitable detergent as indi-
cated in Cap. 6 - Maintenance / Diagnostics
/ Repairs.