W202 C220CDI 1999 Fan runs 24/7

[touchwoodsden]

I have a W202 C220CDI 1999 Diesel Estate with factory aircon. Day before yesterday the main cooling fan didnt switch off with the engine. Unusual as it's never done it before. I thought it may be a on a timer. Well it isnt and it flattened the battery by the end of the day! The fan now runs 24/7 even with the ignition off.
I pulled the 60amp fuse (big fan!) and the fan obviously stopped. There is only one fan fuse on my car.
At least it's winter so little problem at the moment but I do need to get it sorted.
Is it likely to be the temp switch or a relay? If anyone makes any suggestions, can they tell me where the parts are please so that I can pull them? I pulled all relays under the fuse box and inside the mgt box to no avail.

While I am lurking here, the heater plug warning light stays on for 30-90 secs after I start. Any suggestions? The car starts and runs perfectly. A sticky relay I guess but where is it?

1st part of VIN is WDB2021932F.

Thanks for any advice.
TwD

 

[Aussie Nick]

There are some trick hidden relays on the W202.There is another fuse box in the boot next to the battery. At that location there is one relay. I think the colour is blue. However if you take the screws out of the main plastic fuse surround in the engine compartment you will discover a heap of relays under the blanked off section (I think there are 6 or 8 black self taping screws to hold the fuse surround on) . One of those relays has to have a plastic restrainer cap flipped backwards before it can be released.
If you go to the other side of the engine compartment , you will observe a blanked off plastic box.Take all the black screws out and the blanked off cover should then be removed. You will observe some more heavy fuses in this area and possibly a couple of relays.
Regards Aussie nick
PS The information supplied above relates to a petrol W202.I would not expect that the electricals are different on a diesel version or at least significantly different.

 

[television]

The control box for the fan is under the bumper nearside, the chances are is that it is full of water, you can try and dry it out and re seal it.

 

[touchwoodsden]

The control box for the fan is under the bumper nearside, the chances are is that it is full of water, you can try and dry it out and re seal it.

Thanks Malcolm. I looked under the bumper but couldnt see it. Do you have to remove it (the bumper?). I assume that NS means LHS sitting in the car. Where in relation to the headlmap. I seem so thick. When I see it I will feel an idiot I am sure.. "There it was all the time"
Thanks

Nick, There is no relay that I can see in the boot area by the fuses. I pulled all those under the bonnet, under the various plastic covers with no effect.
Thanks

james

 

[television]

http://forums.mercedesclub.org.uk/showthread.php?t=24161&highlight=202+fan&page=2

http://forums.mercedesclub.org.uk/showthread.php?t=25666&highlight=202+fan


No you do not take the bumper off, see if you can find some thing in the 2 links

 

[Aussie Nick]

James .The problem with relays is that you cannot see if they are crook by looking at them as with a fuse. You may try working out the relay likely to be responsible and testing this with a multimeter to see if it is alive. Sometimes relays will trick you by resurrecting when you test them and then jumping back into malfunction mode when your test has been completed. A sign of looming malfunction is usually a rattling sound coming from the relay concerned. Can A member with a wiring diagram of your diesel 202 help out as this would assist you in finding the relay most responsible . I know that the information in the fuse boxes gives no assistance as to where to look.

 

[Aussie Nick]

James . I just had a look at the wiring coming from the cooling fan on my 202. There is a white and blue wire.These wires are shielded back into a main harness leading back across the passenger side guard into the blanked off box in front of the passenger side windscreen. This is where there is a removal port for diagnostic testing. I suspect your culprit relay( if this is the problem) is located in this area. Have a look at the relay connected to the white and blue wire in this area.
Ps I notice that Malcolm is off air. NEAR SIDE means passenger side. Commonly created as NEAR SIDE to the kerb.

 

[television]

No I am on air, With my post the water light comes on in the dash. so Aussie Nick post may be better than mine, I dont care who is right or wrong, the main thing is to try and get you sorted out, and thanks for the help Nick

 

[touchwoodsden]

Thanks for help guys. I had to fit new brake pads tonite so investigated ECU "behind bumper". It isnt so much behind the bumper as between plastic inner wing and bumper. Accessed from under wing. So, caked in crud. I removed it. All seemed dry. Cleaned outside. 2 (diag opposite) screws screws sheared OOps. Got the gubbinge out and warmed it. looked as dry as a bone but, what the heck. It was apart anyhow. All conns dry too. Cleaned studs on car (does it need earth?). Sealded with silicone and 2 screws. Even with lots of heat I couldnt get the 2 stuck ones out so it had to go back with 2 cover screws. Lots of silicone on outside. Refitted. Works a treat but will die at some stage I guess. I least I know that is deffo the p[roblem. Thanks again guys. I wouldnt have dun it without you and sthis site. I will search for ECU at right price. At least there's no rush in winter!
It's fitted away from bonnet heat I guess. It would be better actually behind bummper instead of inside wing. ;-)
james

 

[Aussie Nick]

James Just a word of warning on the silicone. It is not totally foolproof and is known to conduct electricity when wet. Suggest maybe next time you consider a shhrinkwrap shield which is inexpensive and more reliable........Also less gunky on the hands and tools.

 

[television]

Thanks for help guys. I had to fit new brake pads tonite so investigated ECU "behind bumper". It isnt so much behind the bumper as between plastic inner wing and bumper. Accessed from under wing. So, caked in crud. I removed it. All seemed dry. Cleaned outside. 2 (diag opposite) screws screws sheared OOps. Got the gubbinge out and warmed it. looked as dry as a bone but, what the heck. It was apart anyhow. All conns dry too. Cleaned studs on car (does it need earth?). Sealded with silicone and 2 screws. Even with lots of heat I couldnt get the 2 stuck ones out so it had to go back with 2 cover screws. Lots of silicone on outside. Refitted. Works a treat but will die at some stage I guess. I least I know that is deffo the p[roblem. Thanks again guys. I wouldnt have dun it without you and sthis site. I will search for ECU at right price. At least there's no rush in winter!
It's fitted away from bonnet heat I guess. It would be better actually behind bummper instead of inside wing. ;-)
james

I am so pleased it worked

 

[television]

James Just a word of warning on the silicone. It is not totally foolproof and is known to conduct electricity when wet. Suggest maybe next time you consider a shhrinkwrap shield which is inexpensive and more reliable........Also less gunky on the hands and tools.

Interesting Nick that MB say waterproof it as best as you can, a good answer I think

 

[Aussie Nick]

Agree totally Malcolm..The problem with these vulnerable areas which can never be totally sealed is that the moisture penetration, no matter how minute, will almost immediately commence to corrupt the wiring. The moisture will often travel through the cable commpletely corrupting the wire to the point were it turns black and cannot even be resoldered. Add the slightest hint of salt to the equation and the wiring harness is a throw away within weeks. Anyone who has a boat and uses it in a marine situation will appreciate what i am talking about.

 

[television]

Agree totally Malcolm..The problem with these vulnerable areas which can never be totally sealed is that the moisture penetration, no matter how minute, will almost immediately commence to corrupt the wiring. The moisture will often travel through the cable commpletely corrupting the wire to the point were it turns black and cannot even be resoldered. Add the slightest hint of salt to the equation and the wiring harness is a throw away within weeks. Anyone who has a boat and uses it in a marine situation will appreciate what i am talking about.

Add to that the fact that sometimes water can get in, but cant get out, we have this on the SLK and SL cars with the PSE pump