lsp85

On my 2010 E350 (P2) I hear a slight noise coming from my AC ducts.
When the fan speed is on low and there is little outside noise for distraction, I hear what sounds like little droplets of water hitting a hot frying pan. It almost like a hissss noise that gets louder than softer.

I don't believe its the fan, but rather the AC compressor. If the compressor is OFF, the noise will go away. Recirc has no bearing on it, nor does fan speed or fan duct mode.

Naturally when the dealer listens to it, its not there.

It's definitely not a duct cover having wind by-pass issues, I've had that too. This is strictly internal AC compressor noise.

Help

ImInPA

Unless you can get the dealer to hear it, they will not likely repair it. I would not think you would hear the compressor inside the vehicle. try manually changing the mode of air flow and cylce it through all of the positions a few times. Sometimes the flaps inside the ducts can stick or not seat correctly which can cause the sound you describe. I had a Subaru that would do this every once in a while. Just forcing the flaps to redirect the air would "unstick or seal" whatever what causing the "hiss". Hope this helps. If not, good luck in demonstrating it to the dealer. Once they hear it, I am sure they will fix it. Have you gone and tried another E to see if it makes the same noise you are hearing?

ghostbusters

Any news from your dealership lsp85? I am having the exact same problem on my '08 W204 C200K. The mechanic from my dealership rode shotgun with me and heard the noise. He thinks that he "could" locate the problem by dismantling the entire dash. I am scheduling this sometime next week. Hopefully with some luck and news from your end he could locate the problem more easily.

I will keep you updated once the service is conducted next week.

Happy New Year and greetings from Malaysia!

lsp85

I haven't gone back to the dealer yet but I heard another noise with the blower that maybe the cause.

Regardless if the AC is on or off, when the blower fan indicator bar is one less than max, I notice that the blower "pulsates" with the air flow. Meaning that the fan seems to blow a bit faster, then lower, then faster, etc... I'm not sure if its related to my original complaint, but when I go to the dealer next week this will be another issue for them to fix.

MCF

My AC had a whistle at higher fan speeds. The dealer reset the cabin filter and all was good.

lsp85

I do it tomorrow, what an easy fix if it applies Thanks

Tjdehya

I had service B done last week. I got it back from the dealer with a whistle.
I took it back to them and they replaced the cabin filter and the whistle was gone.

MA-E320

+1. Same here. Was told that a misplaced cabin air filtler will cause the whistling noise.

ghostbusters

Finally, the whistling noise is gone! I had the dealer top up my air-con gas and voila! Nothing else was done to the vehicle, apart from the standard - check for leaks.

hyperion667