Generac Power Systems 7 kW NG, 10 kW LP Test 16 Check Stepper Motor Control V-twin Engine Units

Section 2.4

Diagnostic tests

Part 2

AC generators

SECONDARY

ADJUST SCREW

GOVERNOR

SHAFT

GOVERNOR

CLAMP BOLT

PRIMARY ADJUST SCREW

Figure 10. Engine Governor Adjustment Single

Cylinder Engines

PROCEDURE

(8 kW Units with dual governor springs):

1.Loosen the governor clamp bolt (Figure 10).

2.Hold the governor lever at its wide open throttle position, and rotate the governor shaft clockwise as far as it will go. Then, tighten the governor lever clamp bolt to 70 inch-pounds (8 N-m).

3.Start the generator; let it stabilize and warm up at no-load.

4.Connect a frequency meter across the generators AC output leads.

5.Turn the primary adjust screw to obtain a frequency reading of 61.5 Hz. Turn the secondary adjust screw to obtain a frequency reading of 62.5 Hz.

6.When frequency is correct at no load, check the AC voltage reading. If voltage is incorrect, the voltage regulator may require adjustment.

RESULTS:

1.If, after adjusting the engine governor, frequency and voltage are good, tests may be discontinued.

2.If frequency is now good, but voltage is high or low, refer back to flow chart.

3.If engine was overspeeding, check linkage and throttle for binding. If no governor response is indicated refer to engine service manual.

4.If engine appears to run rough and results in low fre- quency, proceed to Problem 18, Section 4.3.

Test 16 – Check Stepper Motor Control (V-twin Engine Units)

PROCEDURE:

1.Remove air cleaner cover to access stepper motor.

2.Physically grab the throttle and verify the stepper motor, linkage and throttle do not bind in any way, if any binding is felt repair or replace components as needed. Some resistance should be felt as the stepper motor moves through it’s travel.

3.Physically move the throttle to the closed position by pulling the stepper motor arm towards the idle stop. See Figures 11 and 12 (for 9/10 kW units) or Figure 13 (for 12-20 kW Units).

4.Place the AUTO-OFF-MANUAL switch to MANUAL and watch for stepper motor movement. It should move to the wide open position during cranking. Once the unit starts the stepper motor should move the throttle to a position to maintain 60 Hertz.

5.If no movement is seen in Step 4 remove the control panel cover. Verify the six pin connector on the printed circuit board is seated properly, remove the connector and then replace it and test again. Verify the switches are correctly set.

6.If problem continues the remove six pin connector from the printed circuit board. Set Volt meter to measure ohms. Carefully measure from the end of the six pin harness as follows:

NOTE: Press down with the meter leads on the connectors exposed terminals, do not probe into the connector.

a. Connect one meter lead to Red, connect the remaining test lead to Orange, approximately 10 ohms should be measured.

b. Connect one meter lead to Red, connect the remaining test lead to Yellow, approximately 10 ohms should be measured.

c. Connect one meter lead to Red, connect the remaining test lead to Brown, approximately 10 ohms should be measured.

d. Connect one meter lead to Red, connect the remaining test lead to Black, approximately 10 ohms should be measured.

e. Connect one meter lead to Red, connect the remaining test to the stepper motor case. No resis- tance should be measured INFINITY or Open.

RESULTS:

1.If the stepper motor fails any part of Step 6 replace the stepper motor.

2.If the stepper motor passes all steps replace the Printed Circuit Board.

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