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There's a friend of mine who has a car (2007 Suzuki Swift petrol 1.3L DOHC 92hp) which has been making a whining noise for a while, the alternator belt broke once few months ago, and during it was broken, there was no noise anymore.

When I checked, I found that the loud noise came from the alternator with a smell of burnt rubber, it really sounded like slipping belt, and it started 10 seconds after turning on the engine on the cold, or sometimes when turning on some electrical features like headlamps or when maneuvering at low speed. Thus, there was a load of rubber particles all around the alternator pulley, when it started to whine, the temperature of the pulley rised very quickly, and tension felt from 14.3V to 12.8V when it whined.

I tried to replace the alternator and belt but it didn't improve. I also tried to unplug the alternator, both the 12V and the control cable, but not at the same time, and in both cases, it stopped whining (and charging).

With all I observed, I assumed that I faced an electrical or electronical issue. Some component may need much energy, and to fulfill the needs, the ECU might increase the coils' impedance in order to produce more power (and by too much increasing it, it makes it hard to drive), but I don't know which component is the cause of that. The battery seemed okay though it was old, so I tested with my battery which is 3 months old, full and more powerful anyway, and it still whined.

Which component could induce such a problem? Could it be a bad ground? If you have any suggestion, I'll appreciate it.

Thank you.

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The component at fault is the alternator. When it's charging, it's creating too much drag which is shredding the drive belt. You could check things like the bushing and bearings but to be fair, I'd just fit a replacement item. That is of course assuming that the correct sized belt has been fitted and is correctly tensioned.

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  • Hi, thanks for your answer, but as I said, I already tried to fit a new alternator, and the new belt is a Gates belt meeting the manufacturer requirements. Actually my question is more about what could cause the alternator to be so hard to drive that the belt slips around its pulley and then make it whines, I apologise if my question wasn't clear enough.
    – Alex
    Commented Mar 22, 2019 at 12:04
  • Sorry Alex, I've just re-read your question. I'd be tempted to check with another source that the belt you have is the correct length for the vehicle. I'd also try reducing the tension on the belt (assuming that it can be adjusted).
    – Steve Matthews
    Commented Mar 22, 2019 at 12:07
  • No problem, I've also tried to tighten the belt more than it was before, and then a little less, but it didn't help at all.
    – Alex
    Commented Mar 22, 2019 at 12:47
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    Relative alignment of the pulleys can cause belt problems; This may be more of a problem with "V" belts.
    – blacksmith37
    Commented Mar 22, 2019 at 16:00
  • Pulleys look well aligned, I don't know how they would have become misaligned, so, sadly, I'm pretty sure it's not the cause of this problem. Thank you anyway.
    – Alex
    Commented Mar 25, 2019 at 7:21

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