Whitey92Lx

I have been noticing a faint chirping sound coming from the passenger side dash on my 2009 C300. The noise frequency seems to accelerate when the car accelerates. It is not brakes or suspension as other threads seem to point toward and is definitely coming from inside the passenger side dash area. Has anyone ever been able to pin point what is causing this issue?

biltrite88

I have heard this same noise in my 2009 c300 4matic.

Mine only occurs when the AC is on and may be something to do with the defrost. It's very intermittent. Almost always happens when my car is warming up in the AM and then goes on and off after about 5 mins of warm-up. I have noticed that if it is not "chirping" and I hit the brakes it will start, then stop when I let off the brakes. Like the OP said, it's definitely not the brakes making the noise, it's inside the car, but it does seem to be triggered by braking sometimes.

To elaborate on the sound, it sounds like something that rotates inside the AC system is not lubricated properly and is squealing or chirping. For me it started happening when it got cold here in MN so I was blaming it on cold parts/lubrication which would explain why it went away after warm up but does not explain the braking correlation.

Whitey92Lx does this sound like the same scenario when you hear the sound?

Whitey92Lx

Yeah that pretty much describes it. I was originally thinking it may be a squeaky fan motor but if that were the case, I don't understand why the frequency or speed of the noise would change while the car is accelerating.

aussie e55

chirping or if clicking maybe stepper motor which opens & shuts air con vents ?.

Glyn M Ruck

It's usually the HVAC blower. Many threads in this regard. Try & lubricate the squirrel cage bearings.

biltrite88

Thanks Glyn! I found this thread, I'll give it a shot this weekend.

https://mbworld.org/forums/c-class-w...yone-else.html