Cooling fan staying on for way too long.

[scotth_uk]

Hi All,

Went downstairs this morning and jumped in the xfire, to hear that the electric fans were still on after parking the car at abour 9:30pm last night. Second time this has happened in two days.

Called the old man back in Oz, who mentioned that the control unit for these in a Merc engine bay is in a place that is easily affected by moisture. He said that a lot of C classes had been back to the dealers after long rain periods with this very problem, and that the SLK320 running gear has the same setup

Anyone had this issue? I did wash the car a couple of times, but would be surprised if I managed to wet the unit.

 

[Steve_Perry]

Can't say I have had this problem. But then I'm guessing you're looking for comparisons against W203's and not W202's. Come to think of it I've never heard a W202 cooling fan remain on after switch off. Heard it on other manufacturers though. Does the W203 have this feature then?

S.

 

[Tigger]

I had this very issue on my W210.

The "Auxilliary Fan Control Unit" is located somewhere behind one of the headlamps and yes this problem is usually caused by moisture penetration.

When my issue was diagnosed surprise surprise the part was on back order so in the meantime I had to disconnect the fans manually once the car had cooled down. I couldn't bring myself to drive around with them permanently disconnected.

 

[scotth_uk]

Thanks for letting me know Tigger. I knew I would't be the only one!

 

[silverarrow]

yep electronic control unit relay under the passenger wheel arch front prone to failure due to water on the seal can cause the fan not to turn at a high speed and effect the temperature ie above 90 if fan stays on then i have read on mbz american site that it will run down the batt fuse can be removed as a temp measure best option new relay yes they are on back order from germany but chassis no given to mbz main agent will give you the del date ie about a week many many c class owners have duff relays and do not understand why fan turns slow and temp rises high or fan on all the time NB NO FAULT CODE WAS STORED ON THE OBC TYPICAL JUST LIKE THE MAF SENSOR NO CODE UNLESS TOTALLY DUFF

 

[Apial]

W124 300CE24 a/c cooling fan relay

I had the same problem today with my 300CE24v. On switching the car off the two electric condensor rad fans continued to run. In the end I had to unplug them using a connector plug clipped to the chassis under the ABS unit area.

When I got home I unscrew the relay box behind the fuse box, 6 screws, and yanked out the offending relay. The relay contacts had lightly stuck together. A simple tap and they were freed up again. I gave a light sand with 800 grade, and all works well so far.

Just in case,I ordered a new relay for £13.33 +vat. I like problems that are cheap to fix!