Paronoff

Starting to warm up in Southern California so turned the A/C on. Air cold. Fan speeds work but slight whistling sound from right side of dash. Sounds like wind noise but still happens when car is stopped. Doesn't seem to get louder by increasing fan speed. Anyone know what could be causing this?

Plutoe

To help eliminate any guess work, I would suggest that you go to the stickies and do the AC actual value test and fault test----then post the results. Good Luck!!

mtrevelino

I know that this is a dumb suggestion, but are ALL the air vents open? In my e320, sometimes my wife will shut off her window vent, and at times the system will whistle.
Mike T.

Plutoe

bump!!

Paronoff

I will check on the vents and run the diagnostic and report back.

Paronoff

Tested unit. No faults. Passenger side vent open. Starting to sound like fan noise. I noticed at higher fan rpm noise goes away.

Plutoe

Could be a leaf or something stuck between fan and filter producing the ole baseball card noise over bicycle spokes!!

mtrevelino

Don't forget to look at the rear vents (if you have any).
Mike T.

Paronoff

I will remove cabin air filters and try some canned air.

track_warrior

You are low on R-134A refrigerant. Go buy a can at autozone and check to see if that solves the problem. My ac started whistling as well, i filled her up and the whistling stopped, it was more of a hissing sound though.

C280 Sport

Yupp. Low on freon will make it sound like a whistling sound or cracking sound too as many described. Also, is the EC light on? If so you are very very low.

Paronoff

No lights no faults. Haven't had a chance to take cabin filters out and blow air through vents. If it doesn't rain this weekend, I will do it and report back.

Paronoff

Still can't find the cause of the intermittent whistle. Ran tests again. Found one fault Eb1. 234. Which I understand is the sun sensor. Turned on air with windshield covered which probably triggered the fault. Cleared it and will re check. Here is latest A/C values.
1 80
2 94
3 40
4 40
5 32
6 184
7 15
8 120

MagCL

Make sure the cabin air filters are installed properly and are clean. I had a whistling as well on my old W220 so I replaced the filters in the glove box and the whistling went away. It's worth a shot!!

Paronoff

First thing I tried. It helped the airflow because the old ones were dirty. I think a tiny twig or leaf is keeping one of the dampers from positioning properly. I hope it is not the passenger side fan. If so, I will fix when it gets worse. Until then the A/C is blowing cold. It is a minor irritation fixed by playing the radio louder. Thank you all for trying to help.

Plutoe

Well you are correct, nothing very obvious with the values except that with a faulty sun sensor your outside air temp sensor seems bad. Those items affect performance.

The other observations are in red---5 should be colder and with 7 at 15, 8 must be 144(law of physics on earth).

Still too early to pinpoint, however knowing the above I would put a set a gauges on the car and look at that data.

MagCL

Your car may have a carbon filter under the dash. Check that as well (if you haven't already).

Paronoff

I will check those but I think I will have a pro look at the A/C system.