The serpentine belt tension may not be correct causing the alternator to slip and squeal. When not tensioned properly, belts are prone to slipping and will cause the alternator to work harder than it should. This excess work will cause the alternator’s bearings to wear prematurely and increase the likelihood of failure. Refer to the manufacturer’s specifications for your vehicle to get instructions and guidance on how to get the correct tension on the belt.
Belt Routing
If the belt is routed incorrectly this could cause the alternator to whine. Check to make sure the serpentine belt is routed according to the vehicle manufacturer’s specifications. Incorrect routing can cause the serpentine belt to rub against other components in the engine bay, causing a whining noise.
Incorrect Belt Size
If the incorrect belt size is used it may cause the belt to slip and the alternator to whine. Verify the serpentine belt size matches the specified size as per your vehicle’s manufacturer recommendations.
Defective Serpentine Belt
Lastly, the belt itself may be defective and cause the alternator to whine. In rare instances, a serpentine belt may come from the manufacture with a manufacturing defect. If after inspecting and correcting all other issues and the alternator continues to whine, you may want to consider replacing the belt with a high quality aftermarket replacement.
