Hi,

I have an electrical humming/whining noise from top of engine bay when key turned to AC - NOT when engine is running.

Otherwise car drives fine with no warning on dash.

Link to video:


Cheers!

 

My son's Mercedes W203 made the exact same noise.The car was running fine. You might want to try to address this problem by replacing the throttle actuator control motor relay.

Check also 13B-631 in the service manual (for V6 engine) if it does not work. The link to the service manual is found in one of the sticky threads in this forum.

 

Get a long screwdriver or other long metal rod. Put one end, handle, of the screwdriver to your ear....place the other end on the device. You will be able to "hear" the noise with much better precision. Kinda works like a stethescope

 

Hi,

I replaced the throttle actuator control motor relay but noise is still there.

Doesn'treally bother me as only happens when car is in ACC.

Any other thoughts?