Whine When Ac Is On?

[Diesegas]

Something weird has just happening. When i'm driving and the engine is at about 3000RPM a whine comes from the engine bay. I was a litle worried at first as i thought it was the transmission. But by chance the other day i turned the AC off when it was making the noise and the sound went away. I opened up the hood, and got my wife to rev the engine to 3000rpm and the sound came from the AC compressor. Odd thing is i only notice it driving round town when i'm on the highway i can't hear it at all. The AC works fine despite this and the compressor turns over smoothly. Would you be worried?

 

[Yah-Tah-Hey]

I would be "worried" (concerned) if anything was "whining."

 

[MolaKule]

I suspect it could be one of two problems:

1. The compressor bearings or compressor pump internals or both are worn

2. Turning on the AC compressor increases belt tension; check tensioner and idle pulley bearings.

 

[Jake_J]

Based on the description it's most likely the AC compressor clutch bearing. You don't hear it on the highway because of the added road/wind noise at higher speeds. It will keep whining until you get the bearing replaced, or if you leave it long enough it will get louder till the point that the bearing fails.

 

[JMJNet]

Depends on the vehicle which you never mention in the Original post, some can just replace the clutch bearing without opening the system.
But that is assuming it is the clutch bearing and not something internal.
Unfortunately, the clutch bearing itself may cost almost the same as the whole compressor but you don't have to recharge the refrigerant.

 

[OppositeLocK]

Hard to tell with video/seeing it in person. But ACs make all kinds of noises.

Fix if/when something breaks. You'll spend more money and time on diagnostics and it may be nothing.