Hey guys, long time BMW and Audi owner, new forum member.

I picked up a low mileage 2004 X5 4.8is recently that is in excellent condition. The dealer was able to confirm my suspicions that this SAV was properly cared for by providing me with the records I requested.

Anyway, as with all vehicles, it was obviously traded in for a reason and I am able to sort pretty much everything myself. I am at the end of the list and this one has me kind of scratching my head. I would appreciate some insight, in case anyone has experienced this one before.

My passenger vents were warm when I bought the vehicle, so I immediately hooked up the manifold gauges and ensured pressures were proper on high and low side (I wish I could have recovered the old stuff and done it the ideal way, but paying someone $250 to recover and sell me back my own refrigerant is ridiculous). After doing this, my a/c is colder, but the passenger vents are still warmer than driver.

I tested for heater valve issues, but it seems that is not it. Passenger vents are slightly warmer regardless of vehicle temp or pinched hose. Interestingly enough, the temp difference between driver and passenger vents increases as I roll the mixture dial colder (to three blue dots).

Also, I checked the Final Stage Resistor and it looked good (Appeared to have been replaced before) and ensured the fins were clean. I checked this because the vents do not blow as hard as I deem a BMW should. My 540 vents blew considerably harder, and these seem to talk the talk (Loud) but they fail to blow hard. Rear vents blow weak and warmer as well. I also noticed slight fluctuations in the fan speed periodically (No indication of change on display, it will just go up and down quickly a few times).

So, my main problem is that I noticed a whistling noise coming from my middle vents today. I isolated the noise to the middle-right as the main culprit and it would lessen with the compressor off. However, if I close the vent then I can faintly hear it from the far right (passenger) vent. If I close BOTH passenger front vents then the noise is GONE. Now, here is the interesting part; when I have all vents open and it is making the whistling noise, I can roll the middle mixture dial and it will go completely quiet when I roll to two blue dots or colder and the same is true when I get past one red dot.

So, for some reason the air mixture dial is controlling the noise issue. And, for the record, the dial gets difficult and wants to spring back when I get all the way to 3 blue dots (It bounces back to around two blue dots). This leads me to believe that there is a stuck actuator or flap down in the dash or something that could be causing my warm front/rear passenger vents and dial issues. I also think the FSR could probably use to be replaced.

I apologize for the book, but it is necessary for the experts here to properly diagnose.

Thanks.

PS It is still 110 degrees here (and humid lately) so I would assume that is amplifying my issues.

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2010 X5 35d
2000 M5 Sport
1999 BMW 540iA Sport
1991 Toyota Pickup - Survivor Garage Queen
2007 750i Sport - SOLD
2007 335i Sport - SOLD
2004 BMW X5 4.8is - SOLD
2004 A4 UltraSport Quattro Manual - SOLD
2001 A6 2.7T Quattro - SOLD