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

**TEST 1: CHECK NO-LOAD VOLTAGE AND FREQUENCY**

The first step in analyzing any problem with the AC generator is to determine the unit's AC output voltage and frequency. This measurement identifies the specific diagnostic path required to resolve the issue (Page 36).

**Required Parameters for Test 1 (at No-Load):**
* **No-Load Voltage:** 122–126 VAC (Page 36)
* **No-Load Frequency:** 61–63 Hertz (Page 36)

**Procedure:**
1. Set a volt-ohm-milliammeter (VOM) to read AC voltage. Connect the meter test leads across customer connection leads T1 (Red) and T2 (White) (Page 36).
2. Disconnect or turn OFF all electrical loads. Initial checks and adjustments are accomplished at no-load (Page 36).
3. Start the engine, let it stabilize and warm up. Read the AC voltage (Page 36).
4. Connect an AC frequency meter across AC output leads T1 (Black) and T2 (White). Repeat the procedure to measure frequency (Page 36).

**Diagnostic Branching (Results):**

* **AC Voltage and Frequency are both "Zero":** Proceed to TEST 12 (Page 36) or GO TO PROBLEM 3 (Page 25).
* **AC Voltage and Frequency are BOTH correspondingly High or Low:** GO TO TEST 2 (Page 36) or GO TO PROBLEM 1 (Page 25).
* *Note: Per Technical Specifications, Operating Speed is 3600 rpm (Page 90).*
* **AC Frequency is GOOD, but Voltage is HIGH:** GO TO VOLTAGE REGULATOR ADJUSTMENT, PAGE 9 (Page 25/36).
* **AC Frequency is GOOD, but LOW or RESIDUALLY indicated:** GO TO TEST 3 (Page 36) or GO TO PROBLEM 2 (Page 25).
* *Note: Residual voltage is defined as approximately 5-12 VAC (Page 36).*
* **No-Load Voltage and Frequency are WITHIN stated limits (122-126 VAC / 61-63 Hz):** Proceed to TEST 13 (Page 36) or GO TO PROBLEM 4 (Page 25).

**Critical Component Specifications (for follow-up testing):**
If branching to winding resistance tests, the following values must be maintained at 68°F:
* **Rotor Winding (Slip Ring to Slip Ring):** 12.72–14.73 ohms (Page 90)
* **Stator Power Windings (11 & 22 / 33 & 44):** 0.468–0.542 ohm (Page 90)
* **Excitation "DPE" Winding (Lead 2 to 6):** 2.168–2.51 ohm (Page 90)
* **Stator Battery Charge Windings (Lead 55 to 77):** 0.15–0.174 ohm (Page 90)

**Load Performance Reference:**
While initial tests are no-load, the unit is rated for the following under 100% load:
* **Voltage (100% Load):** 112.5–116.5 VAC (Page 90)
* **Frequency (100% Load):** 57–60 Hz (Page 90)
* **Rated Max Load (Quietpact 40 G):** 30 AMPERES / 3600 watts (Page 90)

Summary Recommendation: Always verify engine frequency first to ensure the governor is maintaining 61-63 Hertz at no-load before condemning the voltage regulator or stator.