[Coach Mike]

Originally Posted by wwiiavfan

I think this is the air conditioning bleeding pressure. Mine does it too.

Went to the dealer and he said he was not familiar with this after listening to my phone clip of it. Wants to monitor further on Monday, but he thinks it may be related to the AC bleeding pressure too. If it's always been there, I'm still surprised I didn't notice it sooner and that there's not more info on the subject, cuz it sure is annoying ... more now than before I noticed it

We'll know a little more next week I suppose.

[ctrlz]

I do not think it is the A/C bleeding pressure. It goes on for too long. The A/C only takes a few minutes for the pressure to equalize between the high and low sides. And as the pressures get closer to being equal, the frequency of any whistling noise would change.

I was reading in the service manual yesterday, and I am starting to think the sound may be electrical and related to the vehicle sleep state. Anything with a small coil might make a faint whine. Since the car runs on DC, a coil is only likely to make noise if the voltage is PWM'd. Anyway, one of the systems that definitely activates in sleep mode is the vent switch (solenoid) for the charcoal canister, which is part of the EVAP system.

[Coach Mike]

So here's the official response from the dealer:

"After diagnosis and evaluating noise concern - contacted Tech Assistance and sent them video of noise concern. Could feel some vibration on top of fan shroud when vehicle is turned off and A/C has been running. Advise to customer that noise is A/C pressure equalizing and no repairs should be performed as it is a normal characteristic of A/C system."

Appreciate the input and responses here Guys!

[ScatPack]

Thats the sound of the HID ballasts When the HIDs are on. My challenger does that too. Once you turn off the car, the headlights stay on for a few seconds and you can head the ballasts. Then when the headlights turn off, it stops.

[RetRat]

Maybe get a stethoscope with only a rod on the end. I use one for diagnosing electric pump motors for pin pointing bearing noise or other harmonic issues. This should at least get you close to the noise source.