Fan problem - Mercedes-Benz Forum

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post #1 of 1 (permalink) Old 12-18-2013, 09:29 AM Thread Starter
BenzWorld Newbie
Date registered: Dec 2013
Vehicle: slk230 r
Location: spain
Posts: 1
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(Thread Starter)
Fan problem

Hi Guys,

I've put this little essay in the SLK Forum but thought many more heads looking at it might just bring about something new to my fan problem,
Any ideas or thoughts are most welcome.


Hi guys,

I've been under the bonnet all morning with my multi meter and as far as I can tell there is no issue with continuity on the wires that I could see and get to albeit I'm not a sparky mechanic. I've taken out the R170 Relay and the board / solder all looks perfectly normal ie no brown spots of bad or failing solder,
I've taken the Fan module to bits and checked for any sign of the same failing inside, all is looking good inside,
so put everything back together and fired her up and just let her reach her operating temp of 80degs and idled. after a short time sitting at 80degs the needle dropped to 40degs and the fan kicked in for about 10secs or so, then the fan stopped and the temp gauge needle went right back to 80degs, it continued to behave like this for 5 cycles, after which time I was happy that the fan hadn't just continued to run and run and run.
So why would the needle drop to 40 when the fan kicks in and then once it's done it's cooling bit the needle rises back to 80degs.
I've been told more than once that the needle shouldn't drop at all.
Also the coolant temp sensor would appear to have 2 female ends, the sensor itself has 2 open holes inside the casing, the connector also has 2 what appear to be open holes unless of course their are pins that protrude once it's connected ???.

In summary I suppose the main question is ' why does my temp gauge needle drop when the fan kicks in '. and is it anything to get overly worried about, at no time has the car overheated or given me any warning visual or audible, I do get a little nervous when I see the temp gauge needle going back and forth between 40 and 80degs and the fact that the fan does seem to be on for quite a time,
shaneslk230 is offline  
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