W202 Radiator fan issue

[Grey Area]

Hi all. So, as I was stuck in boxing day sales traffic the car began to overheat to the extent that the radiator fan kicked in and the engine coolant level light came on. we're talking about 100-110 degrees on the temp gauge. When I (finally) parked the car and shut the ignition off I noticed that the fan was still running at full speed. I thought this was a little odd but that maybe it would shut off after a minute when the temperature had dropped a little (shows what i know). When I came back a few hours later the fan evidently hadn't shut off until the battery had died. As soon as I connected a jump starter pack to the battery the fan tried to start up again. Now it will not go off and the coolant level light is on even though the levels are fine and the engine is nowhere near hot. Currently have the fan unplugged which solves both problems but I would rather a solution could be found. Prior to this the car has never been a touch over 85 degrees in any scenario. Any help or advice would, of course, be appreciated.

P.S I'm thinking fan control module, any other ideas?

 

[mersum1es]

Check ALL fuses, also in K40 module. Often running fan is due to low/no ecu voltage. Blown fuse may be caused by short circuit in breather heater, inlet flap motor etc.
You are right that faulty fan control module may be culprit too, but I would check more serious sources first.

 

[Grey Area]

Thanks, i'll check them all tomorrow in the day light. Just found this thread that seems to be the same problem, anyone know if this got resolved?

@mersum1es what exactly is the K40 module? Is that the other fuse box in the engine bay?

 

[martyz]

Don't want to state the obvious but.....there is coolant in the system,you have no leaks,the water pump is doing its job,the thermostat is not stuck closed?

 

[Dec]

Bit of a grey area without knowing what year car you have.
This is around 1995 here… Relay Locations

Dec

 

[martyz]

K40 is in front of the ecu passenger side,if thats what you are looking for.

 

[Grey Area]

Thanks martyz and yes don't worry all the levels have been checked and the coolant system is working perfectly. Without the fan plugged in the car is maintaining an almost spot on 85-90 degrees. I believe the initial overheating was a one off caused by heavy traffic or at the very least something I can put a pin in for now. It just seems to have caused other more pressing problems as well.

@Dec, my apologies, the car is a facelift w202 c class (2000) and thanks for the photo.

 

[Dec]

Different from above picture then.

Dec

 

[Grey Area]

So a quick update and a couple of questions to hopefully put this issue to bed. Having checked all the fuses in both fuse boxes and the k40 and found them all to be fine, I had a quick check of the wiring to the fan control module inside the engine bay and all seems well. I then removed the nearside wheel and found the trim that was supposed to be inside the wheel arch, wasn't. This I think caused a massive ingress of dirt and moisture in to the fan control module, which I have removed (see photo).

It makes a sound when shaken like it has water or a large amount of grit in there, but I can't take it apart to look as the screws are seized tight.

So the questions are:
Is there a way to test this thing to make certain it's broken?

Should I source a second hand one of these and how much should I expect to pay?

Is there anything else I can check while I try and source one?

As always, thanks for any help and advice.

P.s sorry about the cr*p photo but it doesn't tell much anyway. So long as someone can tell if I've removed the wrong bit!!!

 

[mersum1es]

Yep, you have right part.

I did not find any obvious but mine was malfunctioning only when asked >50% speed. It can be tested with star, but not always can be pinpointed to control module. Sensor data an be read too, only need to know what they should be (AC ow W210 is diagnosed via HHT, I believe same in W202, and normal star instructions are not available).

I bought second hand, must be sure that get right part number. Could be replaced later by another number, but may not work if taken from wrong car.
And its always possible you get faulty one, like said not clear to test.

 

[guydewdney]

If you get a picture of the location, i could pull the one off my scrapper for you for a modest fee....

 

[Grey Area]

ok, cool. So I think the verdict then is to just slap a second hand one on and see if that works. Probably gonna work out cheaper than putting it on a STAR anyway. Of course that depends on guydewdney's modest fee...

@guydewdney- do you know if the control module was working when you started scrapping your w202? Or did you get it as a non-runner?
And yes, I'll post a photo tomorrow.

 

[guydewdney]

As far as i know it was fine. The car was my daily driver and it all worked. Scrapped due to rust.

Is this in the wheel arch, behind the left headlight, ish?

fan control mercedes | eBay

Seem to be about 20 quid minimum.

20 inc postage?

 

[Grey Area]

Yeah, it was mounted in the passenger side wheel arch, if you removed the front plastic trim it's sort of on the side of the engine bay I think in front of you as you look at it and a little to the left. It has a big multi pin plug thing in one end coming down from the engine bay. I'm sorry I didn't get a photo to upload I was out all day and wasn't able to before it got dark :fail
I can post one up tomorrow if thats ok (he promises this time)

And yeah, that sounds like a deal to me! Thanks very much

due to extremely low post count I don't think i can PM, do you have an email you can PM to me?

P.S the part number if you want to check it's the same part is: A027 545 81 32 / ESG400 / system E 50001.01

 

[guydewdney]

Email is [email protected]

 

[MarkC250]

What worries me is that the engine got hot enough for the fan to come on in the first place,
it suggests that your viscus fan isn't working properly.

 

[Grey Area]

It's an electric fan on my w202 MarkC250, so asfaik theres no viscous coupling involved. Thanks though.

 

[guydewdney]

there should be an engine driven fan too! theres an old thread known iirc as the carrot test for the coupling. Basically, if you can stop the fan using a carrot when its hot, then its u/s. Dont use a finger / spanner as fingers dont grow back, and spanners break the blades, hence the carrot....

 

[MarkC250]

It's an electric fan on my w202 MarkC250, so asfaik theres no viscous coupling involved. Thanks though.

If there is no viscus fan this may be your problem.
Some people remove them in winter for better fuel economy,
I'm sure the C180 should have one as standard, hopefully someone will clarify this.

 

[Dec]

My C180 has no viscus fan just a large electric fan at back of radiator, I have the fan control unit in post #9, never knew what it was until this thread.

My previous 1994 C180 did have the viscus fan.


Dec