Generac Power Systems 941-2, 940-2 service manual Section GENERATOR & SPEED CONTROL SYSTEM, Page

Section 7.1

GENERATOR & SPEED CONTROL SYSTEM

TROUBLESHOOTING REFERENCE CHART

PROBLEM	POSSIBLE CAUSE	REMEDY	PAGE
1. Engine starts, accelerates,	a. Carburetor linkage sticking with	a. Repair sticking throttle	3.4-3
shuts down at 4500 rpm	throttle stuck open.
	b. Stepper Motor failed or seized.	b. Replace Stepper Motor.	3.6-1
	c. Stepper Motor wire connections	c. Reconnect or repair.	3.6-1
	broken or disconnected.
	d. Stepper Motor not properly connected.	d. Reconnect wires.	3.6-1
2. Overvoltage condition and	a. Carburetor linkage sticking with	a. Repair sticking throttle.	3.4-3
speed control system cannot	throttle stuck partly open.
reduce output voltage.	b. Stepper Motor failed or seized.	b. Replace Stepper Motor.	3.6-1
	c. Connection to Stepper Motor is	c. Repair or replace connections.	3.6-1
	broken/disconnected with throttle open.
	d. Stepper Motor not properly connected.	d. Reconnect Stepper Motor wires.	3.6-1
3. Engine speed is maintained	a. Carburetor linkage sticking with	a. Repair sticking throttle.	3.4-3
and no-load voltage is good.	throttle partly open.
However, when load is applied	b. Stepper Motor failed or seized.	b. Replace Stepper Motor.	3.6-1
output voltage drops.	c. Connection to Stepper Motor	c. Repair or replace connections.	3.6-1
	Motor broken or disconnected.
	d. Stepper Motor not properly	d. Reconnect Stepper Motor.	3.6-1
	connected.
4. Engine does not accelerate	a. Carburetor linkage sticking	a. Repair sticking throttle.	3.4-3
when load is applied.	with throttle stuck closed.
	b. Stepper Motor failed or seized.	b. Replace Stepper Motor.	3.6-1
	c. Stepper Motor not properly	c. Reconnect Stepper Motor.	3.6-1
	connected.
5. Engine speed and AC output	a. Stepper Motor failure.	a. Replace Stepper Motor.	3.6-1
voltage erratic under constant	b. Connection to Stepper Motor	b. Repair or replace connections.	3.6-1
load. AC output does not turn	broken or disconnected.
off intermittently.	c. Stepper Motor not properly	c. Reconnect Stepper Motor.	3.6-1
	connected
6. Engine starts but Stepper	a. Stator Timing winding is open.	a. Repair/replace bad wire(s)	1.5-2
Motor does not move. Shut down		TIM1/TIM2 or replace Stator.
occurs after several seconds.	b. Timing winding in Stator shorted	b. Replace Stator.	1.5-2
	to ground.

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