I'm having some weird AC issues on my 2008 FEH, the one in the topic being the primary offender. Here's what's happening:

01) When the fan is turned up almost to (or to) full, there is a loud whistling that seems to be coming from the rear of the vehicle. I initially thought it was coming from the front, but it seems louder toward the back. I suppose it might be reflecting back there, bouncing around a bit and increasing in volume, but I'm not sure.

02) When the fan is on and the AC temperature is set to 70 or above, the front vents stop blowing. I still hear air pressure, but it sounds more like the defogger (although I feel no air flow up there).

I want to take it in to have it looked at, especially as it's relatively new (< 3,000 miles), but I'm in crunch at work and have zero time until middle of next week. If this is a really serious issue, I'll make time to take it in, but I'm hoping it's not too serious and I can just ignore it for a few more days.

Thoughts?

 

I'd guess the whistling is coming from a small air leak at the rear hatch window. Next time it does this, open the flip up window and see if it stops. Sounds like you are pressurizing the cabin with the fan on high.

The second issue sounds like the diverter door is closing for some reason....maybe a vacuum problem. Pain in the neck but make them fix it.

 

You shouldn't be able to pressurize the vehicle with the fan because the air extractors, located on the bottom rear quarters of the vehicle, open under pressure. If these are somehow stuck, you might get a whistle - unlikely.

 

This is a long shot, but I had a Sirius satellite radio installed this past weekend, and the installer did run some wires under the dashboard. He also hooked up the power to the "accessory power" as he called it. Wonder if this could have contributed to these problems...