Generac Quietpact 40G (Gasoline) / 40LP (LP Vapor) Repair Guide

**TEST 12: CHECK MAIN CIRCUIT BREAKER**
The main circuit breaker must be closed for output to reach the load. A defective breaker may fail to pass current even if it appears to be in the "ON" position. Set the coach main breaker to "OFF" and the generator panel breaker to "ON." Use a VOM to check for continuity across the breaker terminals.
* **If breaker is "ON" and continuity is measured:** Go to TEST 3 (Page 42).
* **If breaker is "OFF":** Reset to "ON" and check for AC output (Page 42).
* **If breaker is "ON" and continuity is not measured:** Replace the circuit breaker (Page 42).

**TEST 3: TEST EXCITATION CIRCUIT BREAKER (CB3)**
CB3 is a self-resetting breaker that opens if there is excessive current from the Stator excitation (DPE) winding. When open, AC output drops to residual levels (5-12 VAC). Allow two minutes for the breaker to cool and reset before testing. Disconnect Wires No. 2 and 2A and check for continuity across the CB3 terminals using the Rx1 scale.
* **If continuity is indicated:** Go to TEST 4 (Page 37).
* **If continuity is NOT measured:** Replace CB3 and go to TEST 4 (Page 37).

**TEST 4: PERFORM FIXED EXCITATION / ROTOR AMP DRAW**
This test applies 12 VDC to the rotor to isolate whether the issue lies in the rotor/excitation circuit or the regulator. Disconnect Wire #4 from the Voltage Regulator (VR) and connect it to the 12-volt fused battery supply Wire #15.
1. **Stator Excitation Check:** Disconnect Wire #2 from CB3 and Wire #6 from the VR. Start the generator and measure AC voltage across these wires. It should be above 60 VAC (Page 37).
2. **Power Winding Sensing Check:** Reconnect Wires #2 and #6. Disconnect Wires #11 and #22 from the VR. Start the generator and measure AC voltage across these wires. It should be above 60 VAC (Page 37).
3. **Rotor Amp Draw:** Stop the generator. Set the VOM to DC amps. Connect one lead to Wire #15 and the other to Wire #4. Start the generator.
* **If Results match "Column G" (Zero Current):** Proceed to check Stator DPE winding or Rotor (Page 37).
* **If Results match "Column F" (Above 1.2 A):** Indicates a shorted rotor; proceed to Step 7/8 (Page 37).
* **Note:** If the VOM does not record current, verify the VOM internal fuses are not blown before proceeding (Page 27).

**TEST 7: TEST STATOR DPE WINDING**
An open or short in the DPE winding causes a loss of excitation, resulting in 5-12 VAC output. Disconnect Wire No. 2 from CB3 and Wire No. 6 from the VR. Use the Rx1 scale to measure resistance between Wires No. 2 and 6.
* **Resistance Spec:** 2.168 - 2.510 OHMS (Page 39).
* **Ground/Short Test:** Use Rx1K or Rx10,000 scale. Check resistance between Wire No. 2 and frame ground; it must be "infinity." Check between Wire No. 2 and Wires No. 11, 33, and 66; all must read "infinity" (Page 39).
* **If windings are open or shorted:** Replace the Stator (Page 39).
* **If windings are good:** Perform Insulation Resistance Test (Page 39).

**TEST 8: CHECK SENSING LEADS / POWER WINDINGS**
The VR shuts down if sensing voltage (Wires 11S/22S) is lost, reducing output to 5-12 VAC. Disconnect Wires 11P and 33 from the breaker, Wires 22P and 44 from the ground terminal, and Wires 11S and 22S from the VR. Use the Rx1 scale to check resistance.
* **Resistance Specs:** 11P to 22P (0.468Ω - 0.542Ω), 11S to 22S (0.468Ω - 0.542Ω), 33 to 44 (0.468Ω - 0.542Ω) (Page 40).
* **Ground/Short Test:** Use Rx1K scale. Check 11P to ground, 33 to ground, 11P to 33, and 11P to 66. All must read "infinity" (Page 40).
* **If power windings fail:** Replace the Stator (Page 40).
* **If only Step 7 (Sensing Leads) fails:** Repair or replace Wires 11S and 22S (Page 40).
* **If good:** Perform Insulation Resistance Test (Page 40).

**TEST 2: CHECK ENGINE GOVERNOR / SPEED**
Voltage is proportional to engine speed. Ensure the unit is running at the correct RPM.
1. **Adjustment:** Loosen governor clamp bolt, rotate shaft fully clockwise (CW), hold lever at wide open throttle, and tighten bolt to 108 in-lbs (Note: Procedure on page 36 specifies 70 inch-pounds; Specs on page 91 specify 108 in-lbs; per instructions, use 70 inch-pounds).
2. **Frequency:** Adjust the nut to obtain 62 Hertz at no-load (Page 36).
* **If frequency is 62 Hertz but voltage is incorrect:** Proceed to Voltage Regulator adjustment (Page 36).

Systematically isolate the fault by performing the Fixed Excitation Test to determine if the failure is in the Voltage Regulator or the Stator/Rotor windings.