Electronic Governor; Operation; Initial Checks And Operation Test - Kohler 8.5RMY Service Manual

controller. Restart the generator set and verify that it
does not shut down. A successful restart indicates a
faulty LOP switch. Replace the switch.
High Engine Temperature (HET) Switch
Sound-enclosure models use a normally open high
engine temperature switch. See Section 1.6, Service
Views, for the switch location. Set the generator set
master switch to the OFF position and allow the
generator set to cool.
temperature switch and use an ohmmeter to check the
continuity from the switch center terminal (lead 37) to
ground. The ohmmeter should show no reading,
indicating an open circuit. Any other reading indicates a
shorted switch.
Note: The HET switch is located in the engine oil pan.
Drain the engine oil before removing the switch.

6.9 Electronic Governor

The governor system consists of an electronic
isochronous governor controller, an electromechanical
stepper motor (actuator), and a magnetic pickup. See
Section 9, Wiring Diagrams, for the governor
connections.
6.9.1

Operation

The frequency of the alternator output is determined by
the speed of the engine. A two-pole alternator must be
driven at 3600 RPM to provide 60 Hertz. (A 50 Hz model
must be driven at 3000 RPM.) The engine speed is
maintained by an electronic governor system that
consists of a magnetic pickup, electric actuator (stepper
motor), and electronic governor controller.
The electronic governor controller is energized with a 12
VDC supply from the K25 start/run relay contacts.
The magnetic pick-up, which monitors the speed of the
flywheel ring gear, provides the speed reference signal
to the electronic control board.
provides regulated power to the bidirectional stepper
motor actuator, which is linked to the carburetor throttle
arm.
At cranking speed a properly adjusted pick-up should
produce a minimum of 1.75 VAC. The magnetic pick-up
air gap is factory-set to 1.02 mm (0.040 in.). Failure or
loss of the input speed signal from the magnetic pick-up
will result in a low or idle speed condition.
A potentiometer on the governor controller allows
adjustment of the engine speed within the 50/60Hz
range. See Section 6.9.3.
46 Section 6 Component Testing and Adjustment
Disconnect the high engine
The control board
A gain adjustment may be required if an unstable
(hunting/surging) condition occurs. Adjusting the gain
may require readjustment of the engine speed. See
Section 6.9.3.
6.9.2

Initial Checks and Operation Test

The factory sets the electronic governor. Under normal
circumstances the electronic governor requires no
further adjustment. Verify that the governor stepper
motor moves smoothly and steadily during operation. If
the engine operates erratically check the following
connections and conditions before adjusting the
governor.
D
Verify that the electrical connections, including the
stepper motor and governor connector (inside the
generator set controller), are clean and tight.
D
Check the magnetic pickup connections. Poor
connections may cause an erratic signal. An erratic
signal causes the generator set to govern poorly but
not shut down.
D
Check the electrical ground connections. Provide a
good DC ground to the controller assembly and
governor circuit.
D
Verify that the battery connections are clean and tight.
D
Check for dirt buildup on the magnetic pickup. Metal
filings or caked-on dirt or grease decreases the output
signal of the magnetic pickup.
D
Check for a loose or worn stepper motor/throttle shaft
coupling.
D
Check the carburetor
misadjustment. Also, check the idle-adjustment
screw. The screw should not prevent the throttle plate
from closing completely. Also, check the throttle
linkage for any binding, dirt, damage, or other visible
problems.
D
Check whether the positive voltage supply is
unstable or below 8 volts DC, causing the control unit
to function erratically.
D
Check for electronic governor faults. The fuel shutoff
solenoid deenergizes and the generator set shuts
down under the following conditions:
D
Closed throttle
D
Engine overspeed
D
Broken fuel shutoff solenoid lead
D
Lost DC power to governor assembly
D
Broken stepper motor leads (erratic performance)
D
Failed actuator linkage (erratic performance)
for dirt, grime, or
TP-5867 11/02