What's this noise when the AC is on?

At idle all sounds good, when I turn the AC on, I get a constant chatter. It sounds like its coming from the power steering pump or somewhere between it and the engine. It’s certainly not the compressor which is on the opposite side of the engine. The source of sound radiation seems to be too high up to be the water pump.

Here’s a 26 sec video. It starts out with the AC on for the first 10 seconds, then I turn it off. At the 10 seconds later I turn it back on.
http://qik.com/video/0B5E894FF5E04953825DAA4C49C0A4B5

I tried videoing under the hood, but there was too much noise from the engine and fans to here the noise of mention, but the sound is absolutely not from the compressor or its clutch. I’m confused. Any ideas?

Could be the idler pulley bearing (if so equipped), but most likely the compressor is about to take a dump. Through the years I've had cars that acted similarly. Although, on my '96, I had to replace the compressor because the free-wheel bearing was bad. It was quieter with the A/C on than when it was off.

Check the electric fan. it turn on whenever the compressor is on. you can probably just unplug it and run the ac.

XJ4MEPLZ said:

Check the electric fan. it turn on whenever the compressor is on. you can probably just unplug it and run the ac.

Click to expand...

X2. Easy enough to test too.

It would sure help if you post the engine year. Otherwise, we are all only guessing.

Once again, into the fray...

Buy yourself about 3' of vinyl tubing, 1/2" or less in ID, stick one end in your ear and move the other end around the front of the engine, while it is running--BEING VERY CAREFUL--until you isolate the source of the sound.

MoFo said:

It would sure help if you post the engine year. Otherwise, we are all only guessing.

Click to expand...

2001 4.0L HO

XJ4MEPLZ said:

Check the electric fan. it turn on whenever the compressor is on. you can probably just unplug it and run the ac.

Click to expand...

I'll try it, but if I remember correctly, the electric fan is running with the AC on and off.

heyhar said:

Could be the idler pulley bearing (if so equipped), but most likely the compressor is about to take a dump. Through the years I've had cars that acted similarly. Although, on my '96, I had to replace the compressor because the free-wheel bearing was bad. It was quieter with the A/C on than when it was off.

Click to expand...

Pulley bearing, maybe, but I doubt it's the compressor. The sound is about 15 inches or so away from it.

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