Kohler 11RMY, Service Manual

Page: 59 / 98

TP-5867 11/02 49 Section 6 Component Testing and Adjustment
g. Reinstall the engine blower housing.
h. Reinstall the junction box and housing panels
removed to gain access to the front of the
engine.
6. After adjusting the air gap, check the voltage again
as described in step 4. If the voltage does not
measure 1.75 VAC minimum, replace the magnetic
pickup.
7. To test the governor controller operation,
disconnect the magnetic pickup leads and open
the generator set circuit breaker.
8. Manually move the throttle shaft/governor stepper
motor fully counterclockwise (closed throttle).
9. Start the generator set. The stepper motor should
initially turn clockwise (wide open throttle) and then
turn completely counterclockwise.
The stepper
motor should remain in the counterclockwise
(throttle fully closed) position. If the stepper motor
does not operate as described here, proceed to the
next steps to check the governor and stepper
motor.
10. Place the generator set master switch in the STOP
position. Check for 12 volts at pin 6 and a good
ground connection to pin 10 on the electronic
governor controller.
11. Check the stepper motor coil resistance across
pins 2 and 3 and across pins 1 and 4. Only two
stepper motor leads of each coil group are used
(BLK-YEL and RED-WHT). See Figure 6-20. The
resistance per phase is 38.5 ohms. If one of the
coils has a significantly higher resistance or is
shorted, replace the stepper motor.
12. If there is power and a good ground connection to
the governor controller board and the stepper
motor coil resistances are good, replace the
electronic governor controller.
PIN 3, BLK
PIN 2, YEL
PIN 5, GRN
PIN 4,
RED PIN 1,
WHT PIN 6,
BLUE
SB555
Figure 6-20 Actuator Coil Group
6.9.5 Frequency Adjustment
The engine speed determines the generator output
frequency; 60 Hz units operate at 3600 rpm and 50 Hz
units run at 3000 rpm. Adjust the engine governor to
change the output frequency using the following
procedure.
Frequency Adjustment Procedure
1. Open the generator set line circuit breaker.
2. Attach a frequency meter to the AC output leads.
3. Start and run the generator set until it reaches
normal operating temperature (at least 10 minutes).
4. Adjust the electronic governor speed
potentiometer to obtain a frequency reading of
60 Hz (or 50 Hz on 50 Hz models). The governor
potentiometers are shown in Figure 6-21. Turn the
speed potentiometer clockwise to increase the
frequency and counterclockwise to decrease the
frequency.
Note: Often hunting/surging problems thought to
be caused by the governor are actually
caused by engine or carburetor problems. If
the generator set speed is unstable, hunts,
or surges, check for the cause using the
procedure
in Section 6.9.3 before
proceeding.
5. Check stability with the generator set running and
with no load applied. If the generator set speed is
unstable,
hunts, or surges, turn the gain
potentiometer approximately 1/8 turn
counterclockwise or until the generator set
becomes stable with no hunting or surging.
Observe the frequency reading.
6. Repeat steps 4 and 5 to obtain the rated frequency
and stable operation.
7. Apply rated load to the generator set and observe
the frequency reading. The no load and full load
frequencies should be within 0.4 Hz of the rated
generator frequency; if not, check that the
carburetor throttle plate opens completely without
sticking and check the carburetor adjustment. If
these procedures do not correct the problem,
replace the circuit board.
8. Check for hunting and surging at full load. Turn the
gain potentiometer clockwise in 1/8 turn
increments until the engine hunts and surges.
Then turn the gain potentiometer counterclockwise