ManiacGT

So tonight I got in the car and without ignition on or starting there was a noticeable fan like whirring from the dash that stopped after about a minute. Anyone else noted this? Not sure if it's perhaps the air balance system or something else. It was a bit annoying but then stopped. You can't hear it once the engine is running or the car is moving. At first I thought it might be a fan for the computer but that wouldn't have shut off after a minute of getting in the car. Sounds almost like a failing cooling fan but the car is just a week old.

Glyn M Ruck

When you open the door the CANBus wakes up.

Was the car cold? Was the key in the ignition & had the recognition handshake taken place? If so you might be hearing the excess air fan running for emissions at cold start.

If not then they must trace the noise when the CANBus comes out of hibernation. Could be a noisy HVAC sniffer fan etc.

ManiacGT

Car was cold. Sound was central dash. I'll see if it continues but id rather put up with it than have the dash taken apart or whatever ..

Glyn M Ruck

It might sound like dash but are you sure it's not coming from engine compartment? Excess air fan is in the engine compartment.

ManiacGT

I've not really had chance to look but it sounded mid dash hence wondering if it was air balance related.

Glyn M Ruck

If it's in the dash proper it's likely a cooling fan for Comand, HVAC sniffer fan or a servo or stepper motor that comes on when the CANBus comes out of hibernation. Monitor it. It could be the air balance fan if such a thing exists. I have not pulled a W205 dash apart yet nor do I relish the idea ~ when friends come along with crap jobs like that I usually send them to the dealer. I guess we are all still gaining experience on 205 as a new model. Many things remain the same across many models but there are always some changes with new models. W204 was really old wine in new bottles & mainly 203 below the surface. 205 is a larger step forward.

EDIT: It always amuses me. I've got to be a nutter. I help my friends & people on this forum with their cars but I take my own to the dealer but on the condition that it's under my supervision. My MB owned dealership obliges.

Croc

I have noticed a similar sound which start as soon as I open any of the car door. It's a low humming sound and coming from the overhead control panel. It's not noticeable unless the ambient is very quiet. And the sound goes away after a couple of minutes, accompanied by a very slight shake in the car.

Is this normal?

Glyn M Ruck

If it's the overhead console it is the second HVAC sniffer fan coming on to accurately check inside car temp & normal. Some models have 1 sniffer fan & some 2. Closed top sedans always have one in the overhead console. It blows typical car temp air over the temperature sensor.

ManiacGT

It sounded like it was coming from the top of the dash somewhere behind the comand screen. I could be wrong. I've used the car for two more journeys today and I've not heard it.

Croc

Thx for the reply. Is it suppose to be noticeable or do I have a faulty fan.

Glyn M Ruck

We don't have a lot of W205 experience yet to know what's normal. It depends how sensitive you are. I'm always aware of it if I listen VERY carefully. In day to day use I don't notice it. If you have any doubts get the dealer to check it. Listen to another new car on the floor.

Croc

I notice it easily from within my garage. But it is not noticeable under normal outdoor conditions such as road side or car park. My dealer is on a main road, and at its reception area, the ambient noise was also too much to pick up the sound.

Glyn M Ruck

Sounds as though it's normal. Just monitor it. What I do in cases like this is to ask the dealer to note it at the first service but do nothing. Then you have it recorded by Benz & if it becomes noisier later they have to cover you & fix it.

Croc

Good idea. Thx. I am leaving it alone for now. Will look into it either at the first service.