randsny

I have a 2007 SL550 that I bought used a while back and ever since I have owned the car the radiator fan comes on and is really loud. This starts about 30 seconds after the car is started, even when the engine is cold (it can be below freezing and the fan still come on. I have had it to my Mercedes dealer and they tell me it is normal. I was wondering if any of you have the same thing. Is seem to me the fan should come on when the engine heats up or if I have been driving for a while. It is kind of embarrassing as the fan noise is really noticeable. I have replaced the thermostat assembly and that did not change things. Any ideas on what could cause this?

stykshooter

My SL600 did the same for a few days then an error message came up, "Visit Shop" or something to that affect. Notice a few days later the sound went away but so did the fan. Engine fan stopped working so I replaced engine fan all good, no message.

next2pool

Many times the fan will come on because the AC compressor is running. On our cars the compressor will come on even if it is cold out if the system is set on automatic. If you want to see if that is the case, next time turn the climate control completely off and see if the fan shuts off.

randsny

Thanks next2pool, I have noticed this function as well. When I turn on my AC, the fan runs faster, and when I shut it off it quiets down. The thing is, it seems to be running a lot more than it should. I would think with the AC off and a cold engine (32 degrees), the fan would not come on until the engine is at least up to temp. In my case regardless of engine temp the fan will come on in about 30 seconds and never shut off, just speed up when the AC is on and slow down when I shut it off.

next2pool

Hmmm--that definitely doesn't sound right. Sorry I can't help on that one.

SBundlez

i'm having this issue as well..... as soon as the car turns on its blowing at 300 mph. who's the reason for this, anyone?

moretech

This may be a thermal detector switch, wherever that may be, is bad and is sending an erroneous value to the car computer to activate the fan at the wrong speed. Just my guess but I would think some switch like that seems plausible to control fan speed. Let us all know what comes out of your work as this could help us all for a buggy problem like this

randsny

I have finally found the problem with my radiator fan running at high speeds. A local technician (Eurosports of Wayzata) found that a mouse had made a nest in the front of the car and chewed through some wires that were causing erroneous temperatures on the car. Once the wire were repaired the fan runs normally now. The wires were located in the front of the car on the passenger side. Now when I pull up to a stop sign it doesn't sound like a jet engine waiting to take off.

Bosko Kukucka

That is definatelly not normal. Fan shoud come on to maintain the normal operating temp or AC call. My E350 started doing that and like yours it comes on about 15 sec after engine starts and stays on about 1 minute after the car is shut off completely. In my case I get a codes 10c100 and 10C200 which suggests short circuit at the fan lavel but I did not fix it yet so I can't confirm that that is actually the issue. I will update my post once I fix it.