CL500 W216 rad fan troubles

[Peacheyd]

Hi,

My 2007 CL500 is currently blasting its rad fan when it shouldn't be. On absolute cold start , as soon as the car is unlocked it will spin up and turn on n off every few mins regardless of temperature.

Its winter here and the AC is not being used so I have kinda ruled the compressor out as the problem . I get accurate temp readings on the dash (around 85c at operating temp) so my next guess is the coolant sensor .

Im fairly new ro Mercedes ownership , so I cant quite figure out where the sensor is. The part is fairly cheap at ~£15 but can anyone suggest on how to find and change it? And weather or not I can get away with changing it without draining the coolant?

Or if anyone can suggest any other things to try.
The final option would be the fan relay which I've learnt is part of the fan assembly so means a whole fan change at about £500 , so I'd like to eliminate anything else first .

Thanks advance

 

[alexanderfoti]

Cooling fans on MB's run at full speed when there is a communications issues somewhere on the engine can bus.
They will also run full speed if the AC pressure sensor is giving odd readings that do not make sense vs ambient temperature.

Ideally it needs a diagnostic session on something like Xentry/STAR to pinpoint, I would be going down that route before guessing at the fan controller, much cheaper

 

[LostKiwi]

I'd be guessing at low refrigerant pressure. My 129 did the same till it was regassed.
As Alex says a Star session will soon see.

 

[ajlsl600]

suggest, if yr likely to stick with the brand and have some interest get yrself a star system, IT WILL pay for itself.. if you can find a like minded character to run thru the system with you. saved me ,prob, over a grand last yr, only downside getting familiar with it. i am STILL doing that.

 

[Peacheyd]

I actually really want to get a star system. When I owned a BMW i managed to get INPA set up , but STAR seems really difficult to get as I'm confused by what hardware it needs .

I've checked the bay and Ali Express, but I'm not sure on what to buy. Is it a case of an old XP laptop + a cable or do you need some of the other bits? (Hardware)

I would be very grateful if anyone can shed some light on this .

I think I'll get the AC checked as I see this on every search this issue and see if I can get a STAR system

Thanks

 

[LostKiwi]

Star has 4 main components:
A laptop (with a serial port for earlier version C3)
A multiplexer - essentially a black box that provides the electrical interface between car and laptop.
A cable set - different eras of cars used different connectors
Software - the heart of it all.

As noted C3 uses a serial cable
C4 and C5 are later versions of software and multiplexer which connects wirelessly.

In general a complete kit will come with a laptop with all the software installed, the Mux and cables.

 

[ajlsl600]

plenty about try ebay,guy from hereford supplied mine ,been a stand up guy so far.