Noise from a generator may be caused by a loose drive pulley, loose mounting bolts, worn or dirty bearings, defective diode, or a defective stator. A high frequency whine or magnetic noise may be heard at full output. This is a normal condition.
Perform an output test in order to help distinguish bearing noise from the magnetic noise, also called a whine. Refer to Generator Not Operating Properly . A shorted bridge diode will reduce output to approximately 1/3 of the rating and have a growling noise when at high load. It is also helpful to listen to the generator with a moderate load (engine cooling fans or headlights on) in order to determine if there is a bearing or magnetic noise.
Trouble in the charging system can be detected by the following conditions:
| • | The charge indicator does not light during bulb test, or does not go out after the engine start, or comes back on while the engine is running. |
| • | An undercharged battery as evidenced by a yellow dot in the hydrometer (refer to Battery Hydrometer Displays Dark or Yellow Dot ) or spewing of electrolyte from the vents. |
| • | An overcharged battery as evidenced by spewing of electrolyte from the vents. |
If an undercharged or overcharged battery condition occurs, the following procedure may be used to check the generator drive belt tension.
- Visually inspect the accessory drive belt for damage or looseness.
- Inspect the charging circuit electrical connections for damage or looseness.
- Perform the Generator Electrical Test. Refer to Generator Not Operating Properly .
