Electromechanical Governor System - Kohler 8.5RES Service Manual

6.9 Electromechanical Governor
System
Electromechanical governor systems are used on
models 8.5/12RES and 12TRES.
The governor system consists an electromechanical
stepper motor (actuator) and a magnetic pickup. The
ADC controller controls the governor system operation.
See Section 8, Wiring
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.)
maintained by an electronic governor system that
consists of a magnetic pickup and electric actuator
(stepper motor). The ADC controller controls the
governor system.
The magnetic pick-up, which monitors the speed of the
flywheel ring gear, provides the speed reference signal
to the ADC controller. The controller 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 0.5 mm (0.020 in.). Failure or
loss of the input speed signal from the magnetic pick-up
will result in erratic speed.
A setting on the ADC controller allows adjustment of the
engine speed within the 50/60Hz range.
Section 6.9.3.
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.
84 Section 6 Component Testing and Adjustment
Diagrams, for governor
Engine speed is
See
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.
Verify that the electrical connections are clean and
D
tight.
D Check the magnetic pickup connections. Poor
connections may cause an erratic signal or an
overspeed condition. An erratic signal causes the
generator set to govern poorly but not shut down.
Verify that the battery connections are clean and tight.
D
Check for dirt buildup on the magnetic pickup. Metal
D
filings or caked-on dirt or grease decreases the output
signal of the magnetic pickup.
Check for a loose or worn stepper motor/throttle shaft
D
coupling. Replace the shaft and bushing every 500
hours of engine operation.
Check the carburetor
D
misadjustment. Check for a loose mixer assembly.
D Check the idle-adjustment screw. The screw should
not prevent the throttle plate from closing completely.
Check the throttle linkage for any binding, dirt,
D
damage, or other visible problems.
D Check for electronic governor faults. The fuel shutoff
solenoid deenergizes and the generator set shuts
down under the following conditions:
Closed throttle
D
Engine overspeed
D
Broken fuel shutoff solenoid lead
D
Broken stepper motor leads (erratic performance)
D
Failed actuator linkage (erratic performance)
D
for dirt, grime, or
TP-6196 10/09