Kohler Command CH620 Service Manual page 43

SECOND DESIGN GCU Troubleshooting Electronic Governor
Failure Condition
Target/Selected
Speed not
Maintained
(Overspeed and/or
Underspeed) (No
hunt or surge)
Target/Selected
Speed Not
Maintained (Over
speed and/or Under
speed) (No hunt or
surge)
No Start and/or
ungoverned speed
below 1500 RPM
No response to
selected speed input
24 690 06 Rev. O
Possible Causes
Loss of GCU power When connection is lost, no DLA
(B+ or Ground). movement will be seen. When
(Potentially connection is restored, engine speed
Intermittent) will drop to or below idle speed before
returning to target speed position.
Speed Signal When connection is lost, no DLA
(Potentially movement will be seen. When
Intermittent) connection is restored, throttle returns
to target speed position.
Throttle fully closed. Engine may not start due to closed
No throttle throttle. If engine starts, engine speed
movement. will be below 1500 RPM.
Loss of application GCU regulates engine speed by
supplied speed variable input voltage from a customer-
control input signal. supplied source. When signal is lost,
engine speed will return to idle. When
connection is restored, throttle returns
to target speed position.
Equipment Observations
KohlerEngines.com
Governor System
Inspection/Testing
Test for GCU power by
turning key to ON position
and inspect for LED lights
to illuminate or test GCU
power (red/B+) wire for
supply voltage and test
ground circuit. Inspect all
connections and wires for
poor connection. Repair
and replace as required.
View GCU blink codes for
potential trouble code.
Inspect all connections
and wires for poor
connection. Repair and
replace as required.
Check system power,
physical binding, and
wiring etc.
Conduct speed input wire
(red w/yellow tracer)
voltage test. (Refer to test
description on page 51 for
more information)
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