Whining sound when ac is on
Posted: Fri Oct 23, 2026 2:46 pm
People,
2009 BMW 328i, original owner, 70,000 miles, manual trans. When I shift gears with ac on there is a whining sound that increases with pitch matching the gears I am shifting. The sound matched 100% with the rpm's. But as soon as I turn off the ac button the whining stops.
AC is ice cold. Could it be a bad serpentine belt? Compressor starting to go bad (bearings, etc)? Maybe the spring tensioner on the serpentine belt?
Thanks, People.
2009 BMW 328i, original owner, 70,000 miles, manual trans. When I shift gears with ac on there is a whining sound that increases with pitch matching the gears I am shifting. The sound matched 100% with the rpm's. But as soon as I turn off the ac button the whining stops.
AC is ice cold. Could it be a bad serpentine belt? Compressor starting to go bad (bearings, etc)? Maybe the spring tensioner on the serpentine belt?
Thanks, People.