Hello.
I have a 2015 BMW 550i xDrive with 100,000 miles. There’s a low pitch whine coming from the engine bay when accelerating. It only happens when the AC is on and the whine becomes higher pitched during higher rpms. I figured it’s something to do with the AC unit but don’t know if it’s the belt or the ac compressor. What could the problem be ?
With the engine off, Find a pulley on your alternator, tensioner, even your compressor that you can put a socket on and see if you can turn it without moving the belt. If you can make it spin even with difficulty without moving the belt. You need a new belt. If it doesn’t squeal with the AC off and the belt is tight it’s likely your compressor.
Spray some water in the kelt while engine is running of the noise changed/stopped, you need a new belt.
