Engine cold, not running - Fan activates, full max, when open trunk, unlock door happens again, runs for about 2 minutes, shuts off
While driving, temp normal, fan suddenly activates, full max, shuts off a few minutes later.
No pattern, just activates, regularly at full max speed.

Information: There is no fan relay, fan control module ok, coolant temp sensor, ok - A/C sensor ok.

Any insight appreciated, just spent $800 and got replacement thermostat that seemed to e ok

Fan problem remains?

 

Are you doing the work yourself, and do you have Xentry? If doing the work yourself, my strategy is to replace all parts that are old--you are going to need to eventually anyway--and see where that gets you. If you have Xentry, you may be able to track down the odd electrical behavior. If you don't have Xentry or at least a high quality OBD reader, you are going to need to get one.

 

I vaguely remember something similar happening to my CL when I cleared some codes with the engine not running…try running the engine, re-scan for codes and clear again. This happened to me many years ago so I’m not sure but I think this may help.

 

Unclear whether fan assembly or ECU -- repair guy uncertain

 

https://mbworld.org/forums/s-class-w...ml#post8647419

It did help a previous member, and myself so I figured it was worth a try