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Loud radiator fan

21825 Views 8 Replies 6 Participants Last post by  rudeney
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
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The new fans used on the M272 and M273 engines can be very loud. The one on my CLK sounds like a civil defense siren when it winds up. The control is smart - when the A/C system demands max cold, it will run the fan at full speed. It also runs at full speed when engine temp begins to climb and ambient temp is high. For example, in cooler ambient temps, my engine temp can climb above 90C and the fan just barely runs, but when it's 90F outside, the fan comes on full blast when the engine temp edges over 85C.
This means that it is not getting a signal from the ECU. If the engine starts and runs normally, then it could be a bad temperature sensor, a bad fan control unit (built into the fan) or a wiring issue. You need to get a proper diagnosis bu pulling codes.
It could also be bad temp sensor:

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