I have a 2005 C230. About 30 secs after it starts until about 30 secs after it is turned off it sounds like a jet engine is in there.
It doesn't matter if it is cold or warm when it starts, or if the a/c is on or off. I have located the problem, which is the radiator fan. I have gone through the forums and tried a few things offered. The things I have tried are as follows:
reset the a/c by pushing the defrost and recirc air buttons until the led light quits blinking
moved the fan itself to see if it was stuck, which it wasn't, it turned easily
jiggled the fan back and forth to see if it was loose, it was on correctly
tapped the relay with a screwdriver while the car was running to see if it would adjust, didn't work
changed out the fuse, still didn't change anything
I amabout to pull out my hair, please help
