| Subject: | Isuzu Generator On-Vehicle Diagnostic Testing Procedure |
| Models: | 2007 and Prior Chevrolet W-Series Medium Duty Tilt Cab Models |
| 2007 and Prior GMC W-Series Medium Duty Tilt Cab Models |
| 2007 and Prior Isuzu N-Series Commercial Models |
This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-06-03-008 (Section 06 -- Engine/Propulsion System).
There is a high frequency of generator cores being returned that have been determined to have No Trouble Found after testing. All warranty cores returned to the Hitachi investigation facility are 100% inspected and tested for quality improvement purposes,
including both OEM and remanufactured cores.
Isuzu has provided the following information to aid technicians in properly testing a generator. Replace the generator ONLY if the following tests fail.
Common Symptoms
| • | Battery Discharge Warning Light On |
| • | Noisy Operation (such as belts squealing, worn bearings or brushes) |
Be sure that the belts are not slipping and the battery is fully charged for a valid test. Also, any other electrical condition must be corrected prior to testing. Refer to the Service Manual for specific electrical wiring schematics.
On-Vehicle Testing Procedure
Test the generator using a Charging/Starting System Tester, commonly known as VAT40 or Snap-on MT1552, or equivalent.
- Connect the positive lead of the tester to the positive post of the vehicle's battery, and the negative lead of the tester to the negative post of the vehicle's battery.
- Place the round current-probe cable of the tester onto the B-terminal of the generator.
| • | Test #1 -- Under no electrical load and cold condition with all accessories off (A/C, headlights, radio, wipers) |
| | The regulating voltage should be between 13.5V and 14.8V with the engine running at 2,000 rpm. |
| • | Test #2 -- Under electrical load and cold condition with all accessories still off and the engine running at 2,000 rpm |
| | Increase the electrical load by turning up slowly on the Load controller knob of the tester. |
| - | For a generator rated 80 Amp, the output current should be more than 50A. |
| - | For a generator rated 110 Amp, the output current should be more than 70A. |
Warranty Information
Generators are under the "Basic Coverage" warranty period of 24 months with unlimited mileage.
A Core Tag must be properly completed and returned with the core to minimize delay in receiving core credit.
