Q: Horrible belt squeal when alternator has increased load.

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There is a horrible belt squeal when my alternator is under increased load (headlights on, HVAC, etc). It starts at idle ~800 rpm and gets worse on up to ~3000 rpm where it goes away, only to come back when the engine falls back to idle. Belts are brand new, replaced less than a month ago to try and fix this same issue. It sometimes happens when there is no extra load (everyhting off) but it always happens when there is increased load.

'92 Daihatsu Rocky (Daihatsu not listed in makes)

My car has 126000 miles.
My car has a manual transmission.

Check to be sure all rotating elements are in the same plane. Check belt tension. If all rotating elements are in the same plane, the belt is new and properly tension, then the likely cause is a pulley that has faulty ball bearings or dried out grease. The alternator will have a rear bearing as well that should be checked. If you request a vehicle noise diagnostic - suspect wheel bearings, the responding certified mechanic will pinpoint the origin of the noise and implement the required repairs. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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