[lordbmw]

Recently I've been getting this cyclic "buzzing" noise from the engine.

You can hear it here: https://instaud.io/2XO4

You'll hear the strange sound 3 times in that audio clip (at around 0:03, 0:15, and 0:22)

One thing I did notice is that this strange "buzzing" sound does not happen if I turn off the HVAC system.

The sound is definitely coming from the engine bay. The audio clip was recorded near the engine and not inside the car.

Any ideas on what this could be?

I'm stumped

[Polar Bear]

I figured it had to be something with the compressor so I looked around the internet and found this:

Buzzing Noise- A sign that the AC Compressor is beginning to go bad, a buzzing noise may be heard when turning the AC on. This is usually the sign of an overcharged system, which is only usually an issue when too much Freon is added during an air conditioner service. An overcharged air conditioner will not properly cool and needs to be taken care of as soon as possible. The buzzing is caused by the liquid refrigerant entering the compressor intake port and is a great signifier that there is too much Freon. Replacing the entire air conditioner compressor is expensive and much harder than it initially may look so correcting the issue fast will save you plenty of time and money.

[lordbmw]

Originally Posted by Polar Bear

I figured it had to be something with the compressor so I looked around the internet and found this:

Buzzing Noise- A sign that the AC Compressor is beginning to go bad, a buzzing noise may be heard when turning the AC on. This is usually the sign of an overcharged system, which is only usually an issue when too much Freon is added during an air conditioner service. An overcharged air conditioner will not properly cool and needs to be taken care of as soon as possible. The buzzing is caused by the liquid refrigerant entering the compressor intake port and is a great signifier that there is too much Freon. Replacing the entire air conditioner compressor is expensive and much harder than it initially may look so correcting the issue fast will save you plenty of time and money.

My AC Compressor was replaced recently.

The noise is happening when the A/C is off with the HVAC system turned on - it's heating at this time (not cooling). It's cold outside