Weird noise while AC is on and other weird noise??

For about the last month or two I have been getting a weird noise while the AC is running. The sound appears more when I am having the clutch in or letting it out after switching gears. The noise is best described as some kind of horn/whistling. It sounds like a soft WOOOOOOT. The noise lasts any where from .5 seconds to about maybe 1.5 seconds. And it seems that it only does this when the AC is on, I'm down in Florida and always have the AC on. I am thinking that the AC might need a recharge?? Or a belt is going bad??

Also..another weird noise, when I am sitting stationary with the clutch let fully out sometimes the engine runs louder/rough compared to normal. When it does this, I will push in the clutch fully and then let it out and the sound goes away. Any ideas at all? All help is greatly appreciated. Thanks!

Strange that you should post this, because I'm having the same problem with my A/C.

It seems to get louder when this happens, and I turn it off and everything is fine.

Yeah, when I shut off my AC the sound doesn't occur but like I said...I usually use my AC all the time due to the hot temps down here. I can't figure out what is the cause of the noise.

I get noise #2 (clutch engaged in neutral) all the time lately. I'm not sure what that's about.

My A/C is noisy as well, but it's definitely more of a squeeky belt sound and obviously doesn't go away after a few seconds. I've been ignoring it for the moment...if it goes away when A/C is off, it can't be the serpentine belt itself can it?

Sounds to me that your likely hearing the gears inside your transmission rattle from the engines rough power delivery at idle ( normal ). When the AC is on, the engine has slightly more load and thus slightly more fuel is injected which in turn creates a slightly different harmonic and power delivery to the crankshaft/flywheel. As the transmission gets more age ( and the gear oil too ), the rattley gears become more pronounced. If this truly is the culprit, don't worry about it in the slightest.

Good luck!

edit:

Oh, happy birthday Richard! Your problem does seem to be the belt or the belt tensioner or perhaps even an accessory of some sort ( AC Clutch? ). Good luck to you too!