Well recently I have noticed that when I am stopped at a light in my 03' CL-S, and when my A/C compressor seems to come on I hear this high pitched hum. It does not do it when I am driving only when I am stopped, so I think it might be a vibration...

Any one ever experince this, and if so is there a TSB on it?

i have the same issue. I'm guessing the dealer can handle it

I took my car in when I thought the A/C compressor was really loud when on. Of course they claim normal, but then again, these are the same people who scratched every one of my wheels when mounting my new tires.

It is most likely the accessory belt tensioner pulley. The increased load from the AC compressor will cause it to vibrate more and start a humming or squeaking sound.

A way to check this is to have someone in the car and someone watch the tensioner. Have the AC off and then turn it on. If you can see the tensioner start vibrating more and the sound comes from that region, it is most likely the culprit.

I will try to check that out...althought I must admit that I would not know a belt tensioner if it hit me in the head. I will take a look under the hood...and see if I can find it...Any suggestions on where to look?

Also I have had the belt tensioner re-call completed a while back...maybe they did not tighten it very well.

My AC doesn't just hum, it is so damn loud my kids have begged me not to turn on the AC when they are in the car (when it's on full auto) Service checking it out as we speak. It's been loud for the past couple of months, but the roar is now deafening.

Mine is not that loud, but it is annoying...

Mine does this to since day one well maybe after a month but I never took it in because I know the dealer will either tell me its normal or I mod the car so go fuk yourself. As you can see I do not like my dealer. Try this...if you are at a light and the a/c comes on and hums...hit the brake (I have a 6sd) and see if it stops. Thats what mine does...if its humming at a light I can hit the brake and it stops...sometimes it comes back when I have the foot on the brake still and sometimes it doesnt. But almost every time I hit the brake it stops the humming for at least a couple sec's..

Dealer fixed my AC, according to the typed report it was a broken transistor and blower. They replaced it with a transistor/blower kit. Good as new, no loud noises anymore :-)

Are you sure you guys aren't just hearing the auxilary cooling fan for the A/C? It comes on if the car is sitting still with the A/C on and it is fairly loud.

Maybe I just do not know...I know one thing that another symptom is that when the compressor/ aux fan comes on the car feels like is lerks a bit forward (if I am not pushing the brake very hard) and typically I have to push the brake pedal a little bit harder...

Its not a fan that I hear I dont think...its a definet hum...unless the fan hums. I just dont have it in me tho to go to the dealer and ask them about it...they suck over here big time! It has worked fine for the last 42k miles so im sure its nothing major.

I know exactly what you are talking about with this. A lot of times the car next to me thinks I am trying to get a jump on them because they see my car lunge forward an inch or two if I don't have my foot pressed really hard on the brake. This happens when the heat is on too though, although not to the same degree as the with the A/C.

Well, I checked under the hood today and I found that when the two front fans kick on the humming starts...as soon as the fans go off the humming goes away. It appears that the sound is coming from the area around what appears to be the altinator. The sound is coming from the left side(looking from front) on the engine...in the front somewhere...I am gonna bring the car to the dealer this week and get them to take a look at it. I just figured that I would provide and update.

Art

Sounds like the tensioner pulley and I would bet money on that.

I will make sure to mention that work has been done on the tensioner pully in the past...