So, the weather has turned cooler here in Texas, and with that, I'm noticing some odd behavior from my A/C. I have a few issues that are particularly puzzling to me (FYI, I have an 05 MCSa):

1) Radiator Fan Cycling On and Off: I've noticed that while idling in park (after the water temp and oil temps have reached their normal levels) the water temp rises about a needle width, the radiator fan kicks on, runs for about 30-45 seconds, then kicks off. The process will start again about 2 minutes later. The A/C is not on when this happens and it doesn't happen when the car is cruising. I'd understand this behavior if it were particularly hot outside, but it's been in the 70s and 80s for a while now.

2) Loud Noise Coming from Fan: Over the weekend, I cold started the car, turned on the A/C, and a high-pitched whirring would start immediately -- very audible inside and out. The sound wasn't constant at first, switching back and forth -- in no pattern -- to the normal compressor sound, then it came on constantly until the water and oil temps both reached normal levels. It happened on three cold starts in a row, and hasn't happened since.

3) Louder than Normal Compressor Noise: Okay, this one maybe all in my head. But the overall sound of the A/C seems a lot more intrusive and loud than it did during the summer.

So anyone able to identify with these problems?

 

I had the same problems from my a/c unit. I have manual air conditioning and I have a non-supercharged version. When I would run the a/c I would notice a loud noise unlike the power steering whine, but really annoying. I took the car into my dealership and they ended up replacing my a/c compressor stating that it was shorting in and out and could possibly seize up on me.
If you are still having the same issues please contact David Savell who is my Service manager at mini of Concord, in california and ask him about the a/c issue with my car..
my name is pat

 

i have this same noise...... when increasin' speed it gets louder more so after about 3k rpm's!! it does sound like the compressor is werkin' harder then it needs to be!?!?

 

re #1:, basically,

the fan will come on when the coolant reaches about 210 deg f then turn off when it goes below 205 (approximately)

the fan will run low speed whenever the A/C is on, and if the refrigerant pressure reaches a preset max, the fan will run high.