C350 fan problem

[Steve148]

Need help.
The fan on my c350 2010 starts up a couple of hours after my car has stopped and it sounds like a jet engine, there's no key in the ignition and the fan ramps up and the ramps back down. This happened on Friday and it eventually run the battery down. I sent it to the Mercedes specialist and he said there were no fault codes and couldn't find a problem with it. Got it back yesterday and drove it today for an hour and couple of hours at stand still and it's started up again.
Mechanic said coolant level is fine.
I'm stumped and would love to know what the problem is and what I can do about it please

 

[Steve148]

Anyone had this problem or a resolve ?

 

[Cymruambyth]

I`ve no idea mate but I`m sure someone will have an idea for you.

 

[Uky]

I have C207 where the engine fan runs a short time after engine shut-down (and key out) if the weather is warm and I have been in a traffic jam. (There is also a small electrical coolant pump that runs as well and that one can go on for a long time).

In newer MB's, the engine fan is controlled by the CAN-bus. Should the fan loose contact with the CAN-bus, it enters a "safe" mode and starts running full speed.

Possibly, there is a module fault OR a cable fault that causes this. One unfortunate thing about MB is that some cable harnesses has joints inside the harness (ie. Chassis GND). Such problems are PITA to find.

 

[Steve148]

Well I see a clip on YouTube and it suggested that the problem comes from the battery. So today I had a new battery installed but tonight I have the same problem in the fan coming on once again